[Transcriber’s note: Image sizes are limited to the browser
window size. To expand an image, right click on the image and
select “view image” or “open image in new tab”. Then click
on the new image to see it full size. You could also just
use you favorite image viewer directly.

Many projects are of contemporary interest—magic, kites and
boomerangs for example. Try a
“Querl” for starters.

There are many projects of purely historical interest, such as
chemical photography, phonographs, and devices for coal
furnaces.

Another class of projects illustrate the caviler attitude toward
environment and health in 1913. These projects involve items
such as

asbestos, gunpowder, acetylene, hydrogen, lead, mercury, sulfuric
acid, nitric acid, cadmium, potassium sulfate, potassium cyanide,
potassium ferrocyanide, copper sulfate, and hydrochloric acid.
Many references to these have been highlighted in red.

Projects requiring extra skill and care that involve
high voltage, melting metals, or other hazards, have the title
highlighted.

Please view these as snapshots of culture and attitude, not as
suggestions for contemporary activity.

Be careful and have fun, or simply read and enjoy a trip into
yesterday.]

The Boy Mechanic
Vol. 1
700 Things for Boys to Do
800 Illustrations Showing How

The Boy Mechanic
Vol. 1

Index

How to Make a Glider
(See page 171)

The Boy Mechanic
Volume I

700 Things For Boys To Do

How To Construct

Wireless Outfits, Boats, Camp Equipment,
Aerial Gliders, Kites,
Self-propelled Vehicles Engines, Motors,
Electrical Apparatus, Cameras
And
Hundreds Of Other Things Which Delight Every Boy

With 800 Illustrations

Copyrighted, 1913, By H. H. Windsor
Chicago
Popular Mechanics Co.
Publishers

A Model Steam Engine

Engine Details

The accompanying sketch illustrates a two-cylinder single-acting,
poppet valve steam engine of home construction.

The entire engine, excepting the flywheel, shaft, valve cams,
pistons and bracing rods connecting the upper and lower plates of
the frame proper, is of brass, the other parts named being of
cast iron and bar steel.

The cylinders, G, are of seamless brass tubing, 1-1/2 in. outside
diameter; the pistons, H, are ordinary 1-1/2 in. pipe caps turned
to a plug fit, and ground into the cylinders with oil and emery.
This operation also finishes the inside of the cylinders.

The upright rods binding the top and bottom plates are of steel
rod about 1/8-in. in diameter, threaded into the top plate and
passing through holes in the bottom plate with hexagonal brass
nuts beneath.

The valves, C, and their seats, B, bored with a countersink bit,
are plainly shown. The valves were made by threading a copper
washer, 3/8 in. in diameter, and screwing it on the end of the
valve rod, then wiping on roughly a tapered mass of solder and
grinding it into the seats B with emery and oil.

The valve rods operate in guides, D, made of 1/4-in. brass
tubing, which passes through the top plate and into the heavy
brass bar containing the valve seats and steam passages at the
top, into which they are plug-fitted and soldered.

The
location and arrangement of the valve seats and steam passages
are shown in the sketch, the flat bar containing them being
soldered to the top plate.

The steam chest, A, over the valve mechanism is constructed of
1-in. square brass tubing, one side being sawed out and the open
ends fitted with pieces of 1/16 in. sheet brass and soldered in.
The steam inlet is a gasoline pipe connection such as used on
automobiles.

The valve-operating cams,
F, are made of the metal ends of an old typewriter platen, one
being finished to shape and then firmly fastened face to face to
the other, and used as a pattern in filing the other to shape.
Attachment to the shaft, N, is by means of setscrews which pass
through the sleeves.

The main bearings, M, on the supports, O, and the crank-end
bearings of the connecting rods, K, are split and held in
position by machine screws with provision for taking them up when
worn.

The exhausting of spent steam is accomplished by means of slots,
I, sawed into the fronts of the cylinders at about 1/8 in. above
the lowest position of the piston’s top at the end of the stroke,
at which position of the piston the valve rod drops into the
cutout portion of the cam and allows the valve to seat.

All the work on this engine, save turning the pistons, which was
done in a machine shop for a small sum, and making the flywheel,
this being taken from an old dismantled model, was accomplished
with a hacksaw, bench drill, carborundum wheel, files, taps and
dies. The base, Q, is made of a heavy piece of brass.

The action is smooth and the speed high. Steam is supplied by a
sheet brass boiler of about 3 pt. capacity, heated with a Bunsen
burner.

Contributed by Harry F. Lowe, Washington, D. C.

Magic Spirit Hand

Wax Hand on Board and Electrical Connections

The magic hand made of wax is given to the audience for
examination, also a board which is suspended by four pieces of
common picture-frame wire. The hand is placed upon the board and
answers, by rapping, any question asked by members of the
audience. The hand and the board may be examined at any time and
yet the rapping can be continued, though surrounded by the
audience.

The Magic Wand, London, gives the secret of this spirit hand as
follows: The hand is prepared by concealing in the wrist a few
soft iron plates, the wrist being afterwards bound with black
velvet as shown in Fig. 1. The board is hollow, the top being
made of thin veneer (Fig. 2). A small magnet, A, is connected to
a small flat pocket lamp battery, B. The board is suspended by
four lengths of picture-frame wire one of which, E, is connected
to the battery and another, D, to the magnet. The other wires, F
and G, are only holding wires. All the wires are fastened to a
small ornamental switch, H, which is fitted with a connecting
plug at the top. The plug can be taken out or put in as desired.

The top of the board must be made to open or slide off so that
when the battery is exhausted a new one can be installed.
Everything must be firmly fixed to the board and the hollow space
filled in with wax, which will make the board sound solid when
tapped.

In presenting the trick, the performer gives the hand and board
with wires and switch for examination, keeping the plug concealed
in his right hand. When receiving the board back, the plug is
secretly pushed into the switch, which is held in the right hand.
The hand is then placed on the board over the magnet. When the
performer wishes the hand to move he pushes the plug in, which
turns on the current and causes the magnet to attract the iron in
the wrist, and will, therefore, make the hand rap. The switch can
be made similar to an ordinary push button so the rapping may be
easily controlled without detection by the audience.

Making Skis and Toboggans

Fig.1, 2, 3—Forming the skis

During the winter months everyone is thinking of skating,
coasting or ski running and jumping. Those too timid to run down
a hill standing upright on skis must take their pleasure in
coasting or skating.

The ordinary ski can be made into a coasting ski-toboggan by
joining two pairs together with bars without injury to their use
for running and jumping. The ordinary factory-made skis cost from
$2.50 per pair up, but any boy can make an excellent pair for 50
cents.

In making a pair of skis, select two strips of Norway pine free
from knots, 1 in. thick, 4 in. wide and 7 or 8 ft. long. Try to
procure as fine and straight a grain as possible. The pieces are
dressed thin at both ends leaving about 1 ft. in the center the
full thickness of 1 in., and gradually thinning to a scant 1/2
in. at the ends. One end of each piece is tapered to a point
beginning 12 in. from the end. A groove is cut on the under side,
about 1/4 in. wide and 1/8 in. deep, and running almost the full
length of the ski. This will make it track straight and tends to
prevent side slipping. The shape of each piece for a ski, as it
appears before bending, is shown in Fig. 1.

The pointed end of each piece is placed in boiling water for at
least 1 hour, after which the pieces are ready for bending. The
bend is made on an ordinary stepladder. The pointed ends are
stuck under the back of one step and the other end securely tied
to the ladder, as shown in Fig. 2. They should remain tied to the
ladder 48 hours in a moderate temperature, after which they will
hold their shape permanently.

The two straps, Fig. 3, are nailed an a little forward of the
center of gravity so that when the foot is lifted, the front of
the ski will be raised. Tack on a piece of sheepskin or deer hide
where the foot rests, Fig. 4.

Fig. 4—The Toe Straps

The best finish for skis is boiled linseed oil. After two or
three applications the under side will take a polish like glass
from the contact with the snow.

Fig. 5—Ski-Toboggan

The ski-toboggan is made by placing two pairs of skis together
side by side and fastening them with two bars across the top. The
bars are held with V-shaped metal clips as shown in Fig. 5.

Contributed by Frank Scobie, Sleepy Eye, Minn.

Homemade Life Preserver

Fig. 1, Fig. 2—Inner Tube and Cover

Procure an inner tube of a bicycle tire, the closed-end kind, and
fold it in four alternate sections, as shown in Fig. 1. Cut or
tear a piece of cloth into strips about 1/2 in. wide, and knot
them together. Fasten this long strip of cloth to the folded tube
and weave it alternately in and out, having each run of the cloth
about 4 in. apart, until it is bound as shown in Fig. 1. Make a
case of canvas that will snugly fit the folded tube when
inflated. The straps that hold the preserver to the body may be
made of old suspender straps. They are sewed to the case at one
end and fastened at the other with clasps such as used on overall
straps. The tube can be easily inflated by blowing into the
valve, at the same time holding the valve stem down with the
teeth. The finished preserver is shown in Fig. 2.

How to Make Boomerangs

Bending and Cutting the Wood

When the ice is too thin for skating and the snow is not right
for skis, about the only thing to do is to stay in the house. A
boomerang club will help to fill in between and also furnishes
good exercise for the muscles of the arm. A boomerang can be made
of a piece of well seasoned hickory plank. The plank is well
steamed in a wash boiler or other large kettle and then bent to a
nice curve, as shown in Fig. 1. It is held in this curve until
dry, with two pieces nailed on the sides as shown.

After the piece is thoroughly dried out, remove the side pieces
and cut it into sections with a saw, as shown in Fig. 2. The
pieces are then dressed round. A piece of plank 12 in. wide and 2
ft. long will make six boomerangs. To throw a boomerang, grasp it
and hold the same as a club, with the hollow side away from you.
Practice first at some object about 25 ft. distant, and in a
short time the thrower will be able to hit the mark over 100 ft.
away. Any worker in wood can turn out a great number of
boomerangs cheaply.

Contributed by J. E. Noble, Toronto, Ontario.

How to Make an Eskimo Snow House
By George E. Walsh

Laying the Snow Bricks

Playing in the snow can be raised to a fine art if boys and girls
will build their creations with some attempt at architectural
skill and not content themselves with mere rough work. Working in
snow and ice opens a wide field for an expression of taste and
invention, but the construction of houses and forts out of this
plastic material provides the greatest amount of pleasure to the
normally healthy boy or girl.

The snow house of the Eskimo is probably the unhealthiest of
buildings made by any savage to live in, but it makes an
excellent playhouse in winter, and represents at the same time a
most ingenious employment of the arch system in building. The
Eskimos build their snow houses without the aid of any
scaffolding or interior false work, and while there is a keystone
at the top of the dome, it is not essential to the support of the
walls. These are self-supporting from the time the first snow
blocks are put down until the last course is laid.

The snow house is of the beehive shape and the ground plan is
that of a circle. The circle is first laid out on the ground and
a space cleared for it. Then a row of snow blocks is laid on the
ground and another course of similar blocks placed on top. The
snow blocks are not exactly square in shape, but about 12 in.
long, 6 in. high and 4 or 5 in. thick. Larger or smaller blocks
can be used, according to size of the house and thickness of the
walls.

First, the snow blocks must be packed and pressed firmly into
position out of moist snow that will pack. A very light, dry snow
will not pack easily, and it may be necessary to use a little
water. If the snow is of the right consistency, there will be no
trouble in packing and working with it. As most of the blocks are
to be of the same size throughout, it will pay to make a mold for
them by forming a box of old boards nailed together, minus the
top, and with a movable bottom, or rather no bottom at all. Place
the four sided box on a flat board and ram snow in it, forcing it
down closely. Then by lifting the box up and tapping the box from
above, the block will drop out. In this way blocks of uniform
size are formed, which makes the building simpler and easier.

While one boy makes the blocks another can shave them off at the
edges and two others can build the house, one inside of the
circle and the other outside. The Eskimos build their snow houses
in this way, and the man inside stays there until he is
completely walled in. Then the door and a window are cut through
the wall.

Each layer of snow blocks must have a slight slant at the top
toward the center so that the walls will constantly curve inward.
This slant at the top is obtained better by slicing off the lower
surfaces of each block before putting it in its course. The top
will then have a uniform inward slant.

The first course of the snow house should be thicker than the
others, and the thickness of the walls gradually decreases toward
the top. A wall, however, made of 6-in. blocks throughout will
hold up a snow house perfectly, if its top is no more than 6 or 7
ft. above the ground. If a higher house is needed the walls
should be thicker at the base and well up toward the middle.

The builder has no mortar for binding the blocks together, and
therefore he must make his joints smooth and even and force in
loose snow to fill up the crevices. A little experience will
enable one to do this work well, and the construction of the
house will proceed rapidly. The Eskimos build additions to their
houses by adding various dome-shaped structures to one side, and
the young architect can imitate them. Such dome-shaped
structures are shown in one of the illustrations.

Three-Room Snow House

A fact not well understood and appreciated is that the Eskimo
beehive snow house represents true arch building. It requires no
scaffolding in building and it exerts no outward thrust. In the
ordinary keystone arch used by builders, a, temporary structure
must be erected to hold the walls up until the keystone is fitted
in position, and the base must be buttressed against an outward
thrust. The Eskimo does not have to consider these points. There
is no outward thrust, and the top keystone is not necessary to
hold the structure up. It is doubtful whether such an arch could
be built of brick or stone without scaffolding, but with the snow
blocks it is a simple matter.

Secret Door Lock

Fig. 1, Fig. 2, Fig. 3—The Lock Parts

The sketch shows the construction of a lock I have on a door
which is quite a mystery to those who do not know how it
operates. It also keeps them out. The parts of the lock on the
inside of the door are shown in Fig. 1. These parts can be
covered so that no one can see them.

The ordinary latch and catch A are attached to the door in the
usual manner. The latch is lifted with a stick of wood B, which
is about 1 ft. long and 1 in. wide, and pivoted about two-thirds
of the way from the top as shown. The latch A is connected to the
stick B with a strong cord run through a staple to secure a
right-angle pull between the pieces. A nail, C, keeps the stick B
from falling over to the left. The piece of wood, D, is 6 or 8
in. long and attached to a bolt that runs through the door, the
opposite end being fastened to the combination dial. Two kinds of
dials are shown in Fig. 2. The piece D is fastened on the bolt an
inch or two from the surface of the door to permit placing a
spiral spring of medium strength in between as shown in Fig. 3.
The opposite end of the bolt may be screwed into the dial, which
can be made of wood, or an old safe dial will do. A nail is
driven through the outer end of the piece D and the end cut off
so that it will pass over the piece B when the dial is turned.
When the dial is pulled out slightly and then turned toward the
right, the nail will catch on the piece B and open the latch.

Contributed by Geo. Goodbrod, Union, Ore.

A Convenient Hot-Dish Holder

Holders in a Convenient Place

When taking hot dishes from the stove, it is very convenient to
have holders handy for use. For this purpose I screwed two screw
eyes into the ceiling, one in front of the stove directly above
the place where the holder should hang, and the other back of the
stove and out of the way. I next ran a strong cord through the
two eyes. To one end of the cord I attached a weight made of a
clean lump of coal. The cord is just long enough to let the
weight hang a few inches above the floor and pass through both
screw eyes. I fastened a small ring to the other end to keep the
cord from slipping back by the pull of the weight. I then
fastened two pieces of string to the ring at the end of the cord
and attached an iron holder to the end of each string. The
strings should be just long enough to keep the holders just over
the stove where they are always ready for use, as the weight
always draws them back to place.

Contributed by R. S. Merrill, Syracuse, New York.

Magic-Box Escape

Box with Hinges and Lock.

The things required to make this trick are a heavy packing box
with cover, one pair of special hinges, one or two hasps for as
many padlocks and a small buttonhook, says the Sphinx. The hinges
must be the kind for attaching inside of the box. If ordinary
butts are used, the cover of the box must be cut as much short as
the thickness of the end board. The hinges should have pins that
will slip easily through the parts.

Before entering the box the performer conceals the buttonhook on
his person, and as soon as the cover is closed and locked, and
the box placed in a cabinet or behind a screen, he pushes the pin
or bolt of the hinge out far enough to engage the knob end with
the buttonhook which is used to pull the pin from the hinge. Both
hinges are treated in this manner and the cover pushed up,
allowing the performer to get out and unlock the padlocks with a
duplicate key. The bolts are replaced in the hinges, the box
locked and the performer steps out in view.

A Flour Sifter

When sifting flour in an ordinary sieve I hasten the process and
avoid the disagreeable necessity of keeping my hands in the flour
by taking the top from a small tin lard can and placing it on top
of the flour with its sharp edges down. When the sieve is shaken,
the can top will round up the flour and press it through quickly.

Contributed by L. Alberta Norrell, Augusta, Ga.

A Funnel

An automobile horn with the bulb and reed detached makes a good
funnel. It must be thoroughly cleaned and dried after using as a
funnel.

How to Make Corner Pieces for a Blotter Pad

Manner of Forming the Plates

To protect the corners of blotting pads such as will be found on
almost every writing desk, proceed as follows:

First, make a design of a size proportionate to the size of the
pad and make a right-angled triangle, as shown in Fig. 1, on
drawing paper. Leave a small margin all around the edge and then
place some decorative form therein. Make allowance for flaps on
two sides, as shown, which may later be turned back and folded
under when the metal is worked. It should be noted that the
corners of the design are to be clipped slightly. Also note the
slight overrun at the top with the resulting V-shaped
indentation.

To make a design similar to the one shown, draw one-half of it,
then fold along the center line and rub the back of the paper
with a knife handle or some other hard, smooth surface, and the
other half of the design will be traced on the second side. With
the metal shears, cut out four pieces of copper or brass of No.
22 gauge and with carbon paper trace the shape and decorative
design on the metal. Then cut out the outline and file the edges
smooth.

Cover the metal over with two coats of black asphaltum varnish,
allowing each coat time to dry. Cover the back and all the face
except the white background. Immerse in a solution of 3 parts
water, 1 part nitric acid and 1 part sulphuric acid. When the
metal has been etched to the desired depth, about 1-32 of an
inch, remove it and clean off the asphaltum with turpentine. Use
a stick with a rag tied on the end for this purpose so as to keep
the solution off the hands and clothes. The four pieces should be
worked at the same time, one for each corner.

It remains to bend the flaps. Place the piece in a vise, as shown
in Fig. 2, and bend the flap sharply to a right angle. Next place
a piece of metal of a thickness equal to that of the blotter pad
at the bend and with the mallet bring the flap down parallel to
the face of the corner piece, Fig. 3. If the measuring has been
done properly, the flaps ought to meet snugly at the corner. If
they do not, it may be necessary to bend them back and either
remove some metal with the shears or to work the metal over
farther. All the edges should be left smooth, a metal file and
emery paper being used for this purpose.

If a touch of color is desired, it may be had by filling the
etched parts with enamel tinted by the addition of oil colors,
such as are used for enameling bathtubs. After this has dried,
smooth it off with pumice stone and water. To keep the metal from
tarnishing, cover it with banana-oil lacquer.

Boring Holes in Cork

The following hints will be found useful when boring holes in
cork. In boring through rubber corks, a little household ammonia
applied to the bit enables one to make a much smoother hole and
one that is nearly the same size at both openings. The common
cork, if rolled under the shoe sole, can be punctured easily and
a hole can be bored straighter. The boring is made easier by
boiling the cork, and this operation insures a hole that will he
the desired size and remain the size of the punch or bit used.

Self-Lighting Arc Searchlight

Arc in a Large Can

A practical and easily constructed self-lighting arc searchlight
can be made in the following manner: Procure a large can, about 6
in. in diameter, and cut three holes in its side about 2 in. from
the back end, and in the positions shown in the sketch. Two of
the holes are cut large enough to hold a short section of a
garden hose tightly, as shown at AA. A piece of porcelain tube,
B, used for insulation, is fitted tightly in the third hole. The
hose insulation A should hold the carbon F rigidly, while the
carbon E should rest loosely in its insulation.

The inner end of the carbon E is supported by a piece of No. 25
German-silver wire, C, which is about 6 in. long. This wire runs
through the porcelain tube to the binding post D. The binding
post is fastened to a wood plug in the end of the tube. The tube
B is adjusted so that the end of the carbon E is pressing against
the carbon F. The electric wires are connected to the carbon F
and the binding post D. A resistance, R, should be in the line.

The current, in passing through the lamp, heats the strip of
German-silver wire, causing it to expand. This expansion lowers
the end of the carbon E, separating the points of the two carbons
and thus providing a space between them for the formation of an
arc. When the current is turned off, the German-silver wire
contracts and draws the two carbon ends together ready for
lighting again. The feed can be adjusted by sliding the carbon F
through its insulation.

A resistance for the arc may be made by running the current
through a water rheostat or through 15 ft. of No. 25 gauge
German-silver wire.

Contributed by R. H. Galbreath, Denver, Colo.

A Traveler’s Shaving Mug

Take an ordinary collapsible drinking cup and place a cake of
shaving soap in the bottom ring. This will provide a shaving mug
always ready for the traveler and one that will occupy very
little space in the grip.

Homemade Snowshoes

Made from Barrel Staves

Secure four light barrel staves and sandpaper the outside smooth.
Take two old shoes that are extra large and cut off the tops and
heels so as to leave only the toe covering fastened to the sole.
Purchase two long book straps, cut them in two in the middle and
fasten the ends on the toe covering, as shown in Fig. 1. The
straps are used to attach the snowshoe to the regular shoe. When
buckling up the straps be sure to leave them loose enough for the
foot to work freely, Fig. 2. Fasten the barrel staves in pairs,
leaving a space of 4 in. between them as shown in Fig. 3, with
thin strips of wood. Nail the old shoe soles to crosspieces
placed one-third of the way from one end as shown.

Contributed by David Brown, Kansas City, Mo.

Fish Signal for Fishing through Ice

Bell and Battery in a Box

Watching a fish line set in a hole cut in the ice on a cold day
is very disagreeable, and the usual method is to have some kind
of a device to signal the fisherman when a fish is hooked. The
“tip ups” and the “jumping jacks” serve their purpose nicely, but
a more elaborate device is the electric signal. A complete
electric outfit can be installed in a box and carried as
conveniently as tackle.

An ordinary electric bell, A, Fig. 1, having a gong 2-1/2 in. in
diameter, and a pocket battery, B are mounted on the bottom of
the box. The electric connection to the bell is plainly shown.
Two strips of brass, C, are mounted on the outside of the box.
The brass strips are shaped in such a way as to form a circuit
when the ends are pulled together. The box is opened and set on
the ice near the fishing hole. The fish line is hung over a round
stick placed across the hole and then tied to the inside strip of
brass. When the fish is hooked the line will pull the brass
points into contact and close the electric circuit.

Homemade Floor Polisher

A floor polisher is something that one does not use but two or
three times a year. Manufactured polishers come in two sizes, one
weighing 15 lb., which is the right weight for family use, and
one weighing 25 lb.

A polisher can be made at home that will do the work just as
well. Procure a wooden box such as cocoa tins or starch packages
are shipped in and stretch several thicknesses of flannel or
carpet over the bottom, allowing the edges to extend well up the
sides, and tack smoothly. Make a handle of two stout strips of
wood, 36 in. long, by joining their upper ends to a shorter
crosspiece and nail it to the box. Place three paving bricks
inside of the box, and the polisher will weigh about 16 lb., just
the right weight for a woman to use. The polisher is used by
rubbing with the grain of the wood.

Contributed by Katharine D. Morse, Syracuse, N. Y.

Tying Paper Bag to Make a Carrying Handle

Stages in Tying a Bag

In tying the ordinary paper bag, the string can be placed in the
paper in such a way that it will form a handle to carry the
package, and also prevent any leakage of the contents. The bag
must be long enough for the end to fold over as shown in Fig. 1.
The folds are made over the string, as in Fig. 2. The string is
then tied, Fig. 3, to form a handle, Fig. 4.

Contributed by James M. Kane, Doylestown, Pa.

Equilibrator for Model Aeroplanes

Warping the Aeroplane Wings

On one of my model aeroplanes I placed an equilibrator to keep it
balanced. The device was attached to a crosspiece fastened just
below the propeller between the main frame uprights. A stick was
made to swing on a bolt in the center of the crosspiece to which
was attached a weight at the lower end and two lines connecting
the ends of the planes at the upper end. These are shown in Fig.
1. When the aeroplane tips, as shown in Fig. 2, the weight draws
the lines to warp the plane so it will right itself
automatically.

Contributed by Louis J. Day, Floral Park, N. Y.

Repairing Christmas-Tree Decorations

Small glass ornaments for Christmas tree decorations are very
easily broken on the line shown in the sketch. These can be
easily repaired by inserting in the neck a piece of match,
toothpick or splinter of wood and tying the hanging string to it.

Homemade Scroll Saw

Frame Made of a Rod

A scroll saw, if once used, becomes indispensable in any home
carpenter chest, yet it is safe to say that not one in ten
contains it. A scroll saw is much more useful than a keyhole saw
for sawing small and irregular holes, and many fancy
knick-knacks, such as brackets, bookracks and shelves can be made
with one.

A simple yet serviceable scroll saw frame can be made from a
piece of cold-rolled steel rod, 3/32 or 1/4 in. in diameter, two
1/8-in. machine screws, four washers and four square nuts. The
rod should be 36 or 38 in. long, bent as shown in Fig. 1. Place
one washer on each screw and put the screws through the eyelets,
AA, then place other washers on and fasten in place by screwing
one nut on each screw, clamping the washers against the frame as
tightly as possible. The saw, which can be purchased at a local
hardware store, is fastened between the clamping nut and another
nut as shown in Fig. 2.

If two wing nuts having the same number and size of threads are
available, use them in place of the outside nuts. They are easier
to turn when inserting a saw blade in a hole or when removing
broken blades.

Contributed by W. A. Scranton, Detroit, Michigan.

How to Make a Watch Fob

Watch Fob

The fixtures for the watch fob shown—half size—may be made of
either brass, copper, or silver. Silver is the most desirable
but, of course, the most expensive. The buckle is to be
purchased. The connection is to be of leather of a color to
harmonize with that of the fixtures. The body of the fob may be
of leather of suitable color or of silk. Of the leathers, green
and browns are the most popular, though almost any color may be
obtained.

Make full size drawings of the outline and design of the
fixtures. With carbon paper trace these on the metal. Pierce the
metal of the parts that are to be removed with a small hand drill
to make a place for the leather or silk. With a small metal saw
cut out these parts and smooth up the edges, rounding them
slightly so they will not cut the leather or silk. Next cut out
the outlines with the metal shears. File these edges, rounding
and smoothing with emery paper. The best way of handling the
decorative design is to etch it and, if copper or brass, treat it
with color.

For etching, first cover the metal with black asphaltum varnish,
on the back and all the parts that are not to be touched with the
acid. In the design shown, the unshaded parts should not be
etched and should, therefore, be covered the same as the back.
Apply two coats, allowing each time to dry, after which immerse
the metal in a solution prepared as follows: 3 parts water, 1
part nitric acid,
1 part sulphuric acid. Allow the metal to
remain in this until the acid has eaten to a depth of 1/32 in.,
then remove it and clean in a turpentine bath, using a swab and
an old stiff brush. The amount of time required to do the etching
will depend upon the strength of the liquid, as well as the depth
of etching desired.

For coloring silver, as well as brass and copper, cover the metal
with a solution of the following: 1/2 pt. of water in which
dissolve, after breaking up, five cents worth of sulphureted
potassium. Put a teaspoonful of this into a tin with 2 qt. of
water. Polish a piece of scrap metal and dip it in the solution.
If it colors the metal red, it has the correct strength. Drying
will cause this to change to purple. Rub off the highlights,
leaving them the natural color of the metal and apply a coat of
banana-oil lacquer.

An Austrian Top

Parts of the Top

All parts of the top are of wood and they are simple to make. The
handle is a piece of pine, 5-1/4 in. long, 1-1/4 in. wide and 3/4
in. thick. A handle, 3/4 in. in diameter, is formed on one end,
allowing only 1-1/4 in. of the other end to remain rectangular in
shape. Bore a 3/4-in. hole in this end for the top. A 1/16-in.
hole is bored in the edge to enter the large hole as shown. The
top can be cut from a broom handle or a round stick of hardwood.

To spin the top, take a piece of stout cord about 2 ft. long,
pass one end through the 1/16-in. hole and wind it on the small
part of the top in the usual way, starting at the bottom and
winding upward. When the shank is covered, set the top in the
3/4-in. hole. Take hold of the handle with the left hand and the end
of the cord with the right hand, give a good quick pull on the
cord and the top will jump clear of the handle and spin
vigorously.

Contributed by J.F. Tholl, Ypsilanti, Michigan.

Pockets for Spools of Thread

Pockets for Thread

A detachable pocket for holding thread when sewing is shown
herewith. The dimensions may be varied to admit any number or
size of spools. Each pocket is made to take a certain size spool,
the end of the thread being run through the cloth front for
obtaining the length for threading a needle. This will keep the
thread from becoming tangled and enable it always to be readily
drawn out to the required length.

Contributed by Miss L. Alberta Norrell, Augusta, Ga.

Cleaning Leather on Furniture

Beat up the whites of three eggs carefully and use a piece of
flannel to rub it well into the leather which will become clean
and lustrous. For black leathers, some lampblack may be added and
the mixture applied in the same way.

A Baking Pan

Baking Pan without Sides

When making cookies, tarts or similar pastry, the housewife often
wishes for something by which to lift the baked articles from the
pan. The baking tray or pan shown in the sketch not only protects
the hands from burns but allows the baked articles easily to slip
from its surface. The pan is made from a piece of sheet iron
slightly larger than the baking space desired. Each end of the
metal is cut so that a part may be turned up and into a roll to
make handles for the pan.

A wire or small rod is placed between the handles as shown. This
wire is fastened at each end and a loop made in the center. The
pan can be removed from the oven by placing a stick through the
loop and lifting it out without placing the hands inside the hot
oven. The baking surface, having no sides, permits the baked
articles to be slid off at each side with a knife or fork.

A. A. Houghton, Northville, Mich.

A Broom Holder

A very simple and effective device for holding a broom when it is
not in use is shown in the sketch. It is made of heavy wire and
fastened to the wall with two screw eyes, the eyes forming
bearings for the wire. The small turn on the end of the straight
part is to hold the hook out far enough from the wall to make it
easy to place the broom in the hook. The weight of the broom
keeps it in position.

Contributed by Irl Hicks, Centralia, Mo.

Stringing Wires

A string for drawing electric wires into bent fixtures can be
easily inserted by rolling it into a small ball and blowing it
through while holding one end.

A Darkroom Lantern

Darkroom Lantern

Procure an ordinary 2-qt. glass fruit jar, break out the
porcelain lining in the cover and cut a hole through the metal,
just large enough to fit over the socket of an incandescent
electric globe, then solder cover and socket together, says
Studio Light. Line the inside of the jar with two thicknesses of
good orange post office paper. The best lamp for the purpose is
an 8-candlepower showcase lamp, the same as shown in the
illustration. Screw the lamp into the socket and screw the cover
onto the jar, and you have a safe light of excellent illuminating
power.

When you desire to work by white light, two turns will
remove the jar.

If developing papers are being worked, obtain a second jar and
line with light orange paper, screw into the cover fastened to
the lamp and you have a safe and pleasant light for loading and
development. By attaching sufficient cord to the lamp, it can be
moved to any part of the darkroom, and you have three lamps at a
trifling cost.

Preventing Vegetables from Burning in a Pot

Many housekeepers do not know that there is a simple way to
prevent potatoes from burning and sticking to the bottom of the
pot. An inverted pie pan placed in the bottom of the pot avoids
scorching potatoes. The water and empty space beneath the pan
saves the potatoes. This also makes the work of cleaning pots
easier as no adhering parts of potatoes are left to be scoured
out.

A Clothes Rack

Folding Clothes Rack

A clothes-drying rack that has many good features can be made as
shown in the illustration. When the rack is closed it will fit
into a very small space and one or more wings can be used at a
time as the occasion or space permits, and not tip over. The rack
can be made of any hard wood and the material list is as follows:

1 Center post. 1-1/4 in. square by 62 in.
4 Braces. 1-1/4 in. square by 12 in.
16 Horizontal bars. 1 by 1-1/4 by 24 in.
4 Vertical pieces. 1/4 by 1 by 65 in.

Attach the four braces for the feet with finishing nails after
applying a good coat of glue.

The horizontal bars are fastened to the vertical pieces with
rivets using washers on both sides. The holes are bored a little
large so as to make a slightly loose joint. The other ends of the
bars are fastened to the center post with round head screws. They
are fastened, as shown in the cross-section sketch, so it can be
folded up.

Contributed by Herman Fosel, Janesville, Wis.

Homemade Shower Bath

A Shower Bath That Costs Less Than One Dollar to Make

While in the country during vacation time, I missed my daily bath
and devised a shower bath that gave complete satisfaction. The
back porch was enclosed with sheeting for the room, and the
apparatus consisted of a galvanized-iron pail with a short nipple
soldered in the center of the bottom and fitted with a valve and
sprinkler. The whole, after filling the pail with water, was
raised above one’s head with a rope run over a pulley fastened to
the roof of the porch, and a tub was used on the floor to catch
the water. A knot should be tied in the rope at the right place,
to keep it from running out of the pulley while the pail is
lowered to be filled with water, and a loop made in the end,
which is placed over a screw hook turned into the wall. If the
loop is tied at the proper place, the pail will be raised to the
right height for the person taking the shower bath.

The water will run from 10 to 15 minutes. The addition of some
hot water will make a splendid shower bath.

Contributed by Dr. C. H. Rosenthal, Cincinnati, O.

How to Make Small Sprocket Wheels

As I needed several small sprocket wheels and had none on hand, I
made them quickly without other expense than the time required,
from scrap material. Several old hubs with the proper size bore
were secured. These were put on an arbor and turned to the size
of the bottom of the teeth. Hole were drilled and tapped to
correspond to the number of teeth required and old stud bolts
turned into them. The wheels were again placed on the arbor and
the studs turned to the required size. After rounding the ends of
the studs, the sprockets were ready for use and gave perfect
satisfaction.

Contributed by Charles Stem, Phillipsburg, New York.

Pot-Cover Closet

FIG. 1
FIG. 2
Closet for Holding Pot Covers

The sides of the cover closet are cut as shown in Fig. 1 and
shelves are nailed between them at a slight angle. No dimensions
are given as the space and the sizes of the covers are not always
the same. The back is covered with thin boards placed vertically.
The front can be covered with a curtain or a paneled door as
shown.

Contributed by Gilbert A. Wehr, Baltimore, Md.

Aid in Mixing Salad Dressing

Bottle in Stand

Some cooks find it a very difficult matter to prepare salad
dressing, principally mayonnaise dressing, as the constant
stirring and pouring of oil and liquids are required in the
operation. The simple homemade device shown in the accompanying
sketch greatly assists in this work. It consists of a stand to
hold a bottle, the mouth of which rests against a small gate
directly in the rear of the attached tin trough. The weight of
the bottle and the contents against the gate serves as a check or
stopper. If the gate is raised slightly, it will permit a
continuous flow of liquid of the desired amount.

Saving Overexposed Developing Prints

In using developing papers, either for contact printing or
enlargements, you are, by all rules of the game, entitled to a
certain number of overexposed prints, says a correspondent of
Camera Craft. But there is no reason why you should lose either
the paper or the time and trouble expended in making these
prints. By using the following method, you can turn these very
dark prints into good ones.

First: these overexposed prints must be fully developed. Do not
try to save them by rushing them out of the developer into the
short-stop or fixing bath. The results will be poor, and, if you
try to tone them afterward, the color will be an undesirable,
sickly one. Develop them into strong prints, thoroughly fix, and
wash until you are sure all hypo is removed. In my own practice,
I carry out this part of the work thoroughly, then dry the prints
and lay aside these dark ones until there is an accumulation of a
dozen or more, doing this to avoid too frequent use of the very
poisonous bleaching solution. The bleacher is made up as follows
and should be plainly marked “Poison.”

Place the dry print, without previous wetting, in this solution.
It will bleach slowly and evenly, but, when it starts to bleach,
transfer it to a tray of water, where it will continue to bleach.
When the desired reduction has taken place, stop the action at
once by immersing the print in a 10-per-cent solution of borax.
The prints may be allowed to remain in this last solution until
they are finished. A good final washing completes the process.
This washing must be thorough and a sponge or a tuft of cotton
used to clean the surface of the print.

With a little practice, this method of saving prints that are too
dark becomes easy and certain. The prints are lightened and at
the same time improved in tone, being made blue-black with a
delicate and pleasing quality that will tempt you to purposely
overexpose some of your prints in order to tone them by this
method for certain effects. The process is particularly valuable
to the worker in large sizes, as it provides a means of making
quite a saving of paper that would otherwise be thrown away.

An Ironing-Board Stand

Stand Attached to Table

An ordinary ironing board is cut square on the large end and a
slot cut 1-1/2 in. wide and 4 in. long to admit the angle
support. The support is placed against the table and the board is
pressed down against the outer notch which jams against the
table, thus holding the board rigid and in such a position as to
give free access for ironing dresses, etc.

Contributed by T. L. Gray, San Francisco, Cal.

A Desk Blotting Pad

Fig 3 Paper Corners for Blotter Pads

Procure four sheets of blotting paper, preferably the colored
kind, as it will appear clean much longer than the white. The
size of the pad depends on the size of the blotting paper.

Fold four pieces of ordinary wrapping paper, 5 by 15 in. in size,
three times, to make it 5 by 5 in. Fold each one from corner to
corner as shown in Fig. 1 and again as in Fig. 2. Paste the last
fold together and the corner holders are complete. Put one on
each corner of the blotting paper. They can be fastened with a
small brass paper fastener put through the top of the holder. The
blotting paper can be easily changed by removing the holders and
fasteners. Corners complete are shown in Fig. 3.

Contributed by J. Wilson Aldred Toronto, Canada.

Sleeve Holders for Lavatories

Wires Attached to a Lavatory

A very handy article is an attachment on wash basins or
lavatories for holding the sleeves back while washing the hands.
It is very annoying to have the sleeves continually slip down and
become wet or soiled. The simple device shown herewith can be
made with bent wires or hooks and attached in such a way that it
can be dropped out of the way when not in use.

Contributed by L. J. Monahan, Oshkosh, Wisconsin.

Removing Tarnish

A pencil eraser will remove the tarnish from nickel plate, and
the ink eraser will remove the rust from drawing instruments.

How to Make a Brass Bookmark

Fig. 1       Fig. 2
The Pattern and the Finished Bookmark

Secure a piece of brass of No. 20 gauge, having a width of 2-1/4
in. and a length of 5 in. Make a design similar to that shown,
the head of which is 2 in. wide, the shaft 1 in. wide below the
head and the extreme length 4-1/2 in. Make one-half of the
design, as shown in Fig. 1, freehand, then trace the other half
in the usual way, after folding along the center line. Trace the
design on the metal, using carbon paper, which gives the outline
of the design Fig. 2.

Drilling and Sawing the Metal

With the metal shears, cut out the outline as indicated by the
drawing. With files, smooth off any roughness and form the edge
so that it shall be nicely rounded.

The parts of the design in heavy color may be treated in several
ways. A very satisfactory treatment is obtained by etching, then
coloring. Clean the metal thoroughly with pumice stone and water
or with alcohol before the design is applied. Cover all the metal
that is not to be lowered with a thick coating of asphaltum.
Allow this to dry, then put on a second coat. After this has
dried, thoroughly immerse the metal in a solution composed as
follows: 3 parts water, 1 part sulphuric acid,
1 part nitric acid.

Allow the metal to remain in this solution until the exposed part
has been eaten about 1/32 in. deep, then remove it and clean off
the asphaltum, using turpentine. Do not put the hands in the
solution, but use a swab on a stick.

For coloring olive green, use 2 parts water to 1 part permuriate
of iron. Apply with a small brush.

The lines at A and B will need to be cut, using a small metal
saw. Pierce a hole with a small drill, Fig. 3, large enough to
receive the saw and cut along the lines as in Fig. 4. A piece of
wood with a V-shaped notch which is fastened firmly to the bench
forms the best place in which to do such sawing. The teeth of the
saw should be so placed that the sawing will be done on the
downward stroke. The metal must be held firmly, and the saw
allowed time to make its cut, being held perpendicular to the
work.

After the sawing, smooth the edges of the metal with a small file
and emery paper. The metal clip may be bent outward to do this
part of the work.

Cheesebox-Cover Tea Tray

The cover from a cheesebox can be converted into a tea tray that
is very dainty for the piazza, or for serving an invalid’s
breakfast.

First sandpaper the wood until it is smooth, then stain it a
mahogany color. The mahogany stain can be obtained ready
prepared. After the stain has dried, attach brass handles, which
can be obtained for a small sum at an upholsterer’s shop. A round
embroidered doily in the bottom adds to the appearance of the
tray.

Contributed by Katharine D. Morse, Syracuse, New York.

Piercing-Punch for Brass

Drill a 1/2-in. hole through a block of pine or other soft wood 2
in. thick. Tack over one end of the hole a piece of pasteboard in
which seven coarse sewing-machine needles have been inserted. The
needles should be close together and pushed through the
pasteboard until the points show. The hole is then filled with
melted babbitt metal. When this is cold, the block is split and
the pasteboard removed. This tool makes neat pierced work and in
making brass shades, it does the work rapidly.

Contributed by H. Carl Cramer, East Hartford, Conn.

Kitchen Chopping Board

Knife Attached to the Board

Cooks can slice, chop or mince vegetables and various other food
rapidly by placing the little device, as shown, on a chopping
board. Ii is an ordinary staple, driven in just far enough to
allow a space for the end of an ordinary pointed kitchen knife to
fit in it. The staple is driven in the edge of the chopping
board. The knife can be raised and lowered with one hand, as the
material is passed under the blade with the other. Great pressure
can be applied and the knife will not slip.

Contributed by M. M. Burnett, Richmond, Cal.

Carrying Mattresses

Sew straps to the sides of mattresses and they can be handled
much easier.

A Carpenter’s Gauge

Round Stick In a Spool

The home workshop can be supplied with a carpenter’s gauge
without any expense’ by the use of a large spool and a round
stick of wood. The stick should be dressed to fit the hole in the
spool snugly and a small brad driven through one end so that the
point will protrude about 1/16 in.

The adjustment of the gauge is secured by driving the stick in
the hole in the direction desired. A better way and one that will
make the adjusting easy is to file the point end of a screw eye
flat and use it as a set screw through a hole in the side of the
spool.

A Flatiron Rest

Board or Wall Iron Rest

The iron rest and wall hanger shown in the sketch is made of
sheet iron. The upturned edges of the metal are bent to fit the
sloping sides of the iron. The holder and iron can be moved at
the same time.

Contributed by W. A. Jaquythe, Richmond, Cal.

Use for Paper Bags

When groceries are delivered, save the paper bags and use them
for staring bread and cakes. Tie the neck of the bag with a
string and it will keep the contents fresh and clean.

Contributed by Mrs. L. H. Atwell, Kissimmee, Florida.

Use Chalk on Files

If a little chalk is rubbed on a file before filing steel, it
will keep the chips from sticking in the cuts on the file and
scratching the work.

A Homemade Steam Turbine
By William H. Warnecke

Details of the Turbine

Procure some brass, about 3/16 in. thick and 4 in. square; 53
steel pens, not over 1/4 in. in width at the shank; two enameled,
or tin, saucers or pans, having a diameter on the inside part of
about 4-1/2 in.; two stopcocks with 1/8 in. holes; one shaft;
some pieces of brass, 1/4 in. thick, and several 1/8-in. machine
screws.

Lay out two circles on the 3/16-in. brass, one having a diameter
of 3-1/2 in. and the other with a diameter of 2-3/4 in. The
outside circle is the size of the finished brass wheel, while the
inside circle indicates the depth to which the slots are to be
cut. Mark the point where a hole is to be drilled for the shaft,
also locate the drill holes, as shown at A, Fig. 1. After the
shaft hole and the holes A are drilled in the disk, it can be
used as template for drilling the side plates C.

The rim of the disk is divided into 53 equal parts and radial
lines drawn from rim to line B, indicating the depth of the
slots. Slots are cut in the disk with a hacksaw on the radial
lines. A small vise is convenient for holding the disk while
cutting the slots. When cutting the disk out of the rough brass,
sufficient margin should be left for filing to the true line. The
slots should be left in their rough state as they have a better
hold on the pens which are used for the blades. The pens are
inserted in the slots and made quite secure by forcing ordinary
pins on the inside of the pens and breaking them off at the rim,
as shown in Fig. 4.

When the pens are all fastened two pieces of metal are provided,
each about 1 in. in diameter and 1/32 in. thick, with a 3/8-in.
hole in the center, for filling pieces which are first placed
around the shaft hole between the disk and side plates C, Fig. 1.
The side plates are then secured with some of the 1/8-in. machine
screws, using two nuts on each screw. The nuts should be on the
side opposite the inlet valves. The shaft hole may also be filed
square, a square shaft used, and the ends filed round for the
bearings.

The casing for the disk is made of two enameled-iron saucers,
Fig. 2, bolted together with a thin piece
of asbestos between
them to make a tight joint. A 3/4-in. hole is cut near the edge
of one of the saucers for the exhaust. If it is desired to carry
the exhaust beyond the casing, a thin pipe can be inserted 1/4
in. into the hole. Holes are drilled through the pipe on both
inside and outside of the casing, and pins inserted, as shown in
Fig. 5. Solder is run around the outside pin to keep the steam
from escaping. At the lowest point of the saucer or casing a
1/8-in. hole is drilled to run off the water. A wood plug will
answer for a stopcock.

If metal dishes, shaped from thick material with a good coating
of tin, can be procured, it will be much easier to construct the
casing than if enameled ware is used. The holes can be easily
drilled and the parts fitted together closely. All seams and
surfaces around fittings can be soldered.

Nozzles are made of two stopcocks having a 1/8-in. hole. These
are connected to a 3/8-in. supply pipe. The nozzles should be set
at an angle of 20 deg. with the face of the disk. The nozzle or
stopcock will give better results if the discharge end is filed
parallel to the face of the disk when at an angle of 20 deg.
There should be a space of 1/16 in. between the nozzle and the
blades to allow for sufficient play, Fig. 3.

The bearings are made of 1/4-in. brass and bolted to the casing,
as shown, with 1/8-in. machine screws and nuts. Two nuts should
be placed on each screw. The pulley is made by sliding a piece of
steel pipe on the engine shaft and fastening it with machine
screws and nuts as shown in Fig. 6. If the shaft is square,
lead
should be run into the segments.

The driven shaft should have a long bearing. The pulley on this
shaft is made of pieces of wood nailed together, and its
circumference cut out with a scroll saw. Flanges are screwed to
the pulley and fastened to the shaft as shown in Fig. 7.

The bearings are made of oak blocks lined with heavy tin or sheet
iron for the running surface. Motion is transmitted from the
engine to the large pulley by a thin but very good leather belt.

Homemade Telegraph Key

Brass Key on a Wood Base

A simple and easily constructed telegraph key may be made in the
following manner: Procure a piece of sheet brass, about 1/32 in.
thick, and cut out a strip 3-1/2 in. long by 3/4 in. wide. Bend
as shown in Fig. 1 and drill a hole for the knob in one end and a
hole for a screw in the other. Procure a small wood knob and
fasten it in place with a small screw. Cut a strip of the same
brass 2-3/4 in. long and 5/16 in. wide and bend as shown in Fig.
2. Drill two holes in the feet for screws to fasten it to the
base, and one hole in the top part for a machine screw, and
solder a small nut on the under side of the metal over the hole.

Mount both pieces on a base 4-1/4 by 2-3/4 by 1/4 in., as in Fig.
3, and where the screw of the knob strikes the base when pressed
down, put in a screw or brass-headed tack for a contact. Fasten
the parts down with small brass wood-screws and solder the
connections beneath the base. Binding posts from an old battery
cell are used on the end of the base. The screw on top of the
arch is used to adjust the key for a long or short
stroke.

Contributed by S. V. Cooke, Hamilton, Canada.

Keeping Food Cool in Camps

Camps and suburban homes located where ice is hard to get can be
provided with a cooling arrangement herein described that will
make a good substitute for the icebox. A barrel is sunk in the
ground in a shady place, allowing plenty of space about the
outside to fill in with gravel. A quantity of small stones and
sand is first put in wet. A box is placed in the hole over the
top of the barrel and filled in with clay or earth well tamped.
The porous condition of the gravel drains the surplus water after
a rain.

The end of the barrel is fitted with a light cover and a heavy
door hinged to the box. A small portion of damp sand is sprinkled
on the bottom of the barrel. The covers should be left open
occasionally to prevent mold and to remove any bad air that may
have collected from the contents.

Contributed by F. Smith, La Salle, Ill.

Homemade Work Basket

Secure a cheese box about 12 in. high and 15 in. or more in
diameter. It will pay you to be careful in selecting this box. Be
sure to have the cover. Score the wood deeply with a carpenter’s
gauge inside and out 3-1/2 in. from the top of the box. With
repeated scoring the wood will be almost cut through or in shape
to finish the cut with a knife. Now you will have the box in two
pieces. The lower part, 8-1/2 in. deep over all, we will call the
basket, and the smaller part will be known as the tray.

Remove the band from the cover and cut the boards to fit in the
tray flush with the lower edge, to make the bottom. Fasten with
3/4-in brads. The kind of wood used in making these boxes cracks
easily and leaves a rough surface which should be well
sandpapered.

The four legs are each 3/4-in. square and 30-1/2 in. long. The
tops should be beveled to keep them from splintering at the
edges. With a string or tape measure, find the circumference of
the tray or basket and divide this into four equal parts,
arranging the lap seam on both to come midway between two of the
marks. When assembling, make these seams come between the two
back legs.

The tray is placed 1-1/4 in. from the top end and the basket
6-3/4 in. from the bottom end of the legs. Notch the legs at the
lower point about 1/8 in. deep and 1-1/4 in. wide to receive the
band at the lower end of the basket. Fasten with 3/4-in. screws,
using four to each leg, three of which are in the basket. Insert
the screws from the inside of the box into the legs.

Stain the wood before putting in the lining. If all the parts are
well sandpapered, the wood will take the stain nicely: Three
yards of cretonne will make a very attractive lining. Cut two
sheets of cardboard to fit in the bottom of the tray and basket.
Cover them with the cretonne, sewing on the back side. Cut four
strips for the sides from the width of the goods 5-1/2 in. wide
and four strips 10 in. wide. Sew them end to end and turn down
one edge to a depth of 1 in. and gather it at that point,—also
the lower edge when necessary. Sew on to the covered cardboards.
Fasten them to the sides of the tray and basket with the smallest
upholsterers’ tacks. The product of your labor will be a very
neat and useful piece of furniture.

Contributed by Stanley H. Packard, Boston, Mass.

A Window Display

Paper Aeroplanes in Draft

A novel and attractive aeroplane window display can be easily
made in the following manner: Each aeroplane is cut from folded
paper, as shown in the sketch, and the wings bent out on the
dotted lines. The folded part in the center is pasted together.
Each aeroplane is fastened with a small thread from the point A
as shown. A figure of an airman can be pasted to each aeroplane.
One or more of the aeroplanes can be fastened in the blast of an
electric fan and kept in flight the same as a kite. The fan can
be concealed to make the display more real. When making the
display, have the background of such a color as to conceal the
small threads holding the aeroplanes.

Contributed by Frederick Hennighausen, Baltimore, Md.

How to Make a Flint Arrowhead

Fig.2 Fig.3
The Stone Chipped into Shape

If you live where flints abound, possess the requisite patience
and the knack of making things, you can, with the crudest of
tools and a little practice, chip out as good arrowheads as any
painted savage that ever drew a bow. Select a piece of
straight-grained flint as near the desired shape as possible. It
may be both longer and wider than the finished arrow but it
should not be any thicker. The side, edge and end views of a
suitable fragment are shown in Fig. 1. Hold the piece with one
edge or end resting on a block of wood and strike the upper edge
lightly with a hammer, a small boulder or anything that comes
handy until the piece assumes the shape shown in Fig. 2.

The characteristic notches shown in the completed arrow, Fig. 3,
are chipped out by striking the piece lightly at the required
points with the edge of an old hatchet or a heavy flint held at
right angles to the edge of the arrow. These heads can be made so
that they cannot be distinguished from the real Indian
arrowheads.

Contributed by B. Orlando Taylor, Cross Timbers, Mo.

An Opening Handle for a Stamp Pad

Handle on Cover

A stamp pad is a desk necessity and the cleanliness of one
depends on keeping it closed when it is not in use. The opening
and closing of a pad requires both hands and consequently the
closing of a pad is often neglected in order to avoid soiling the
fingers. This trouble can be avoided if the pad is fitted with a
small handle as shown in the sketch. Take the ordinary pad and
work the hinge until it opens freely. If necessary apply a little
oil and spread the flanges of the cover slightly.

Saw off the top of a common wood clothespin just above the slot,
saving all the solid part. Fasten this to the cover near the back
side in an upright position with a screw. A tap on the front side
of the pin will turn it over backward until the head rests on the
desk thus bringing the cover up in the upright position. When
through using the pad, a slight tap on the back side of the cover
will turn it down in place.

Contributed by H. L. Crockett, Gloversville, N. Y.

Concrete Kennel

Finished Kennel

Concrete Forms

The kennel shown in the illustration is large enough for the
usual size of dog. It is cleanly, healthful and more ornamental
than the average kennel. This mission style would be in keeping
with the now popular mission and semi-mission style home, and,
with slight modifications, it could be made to conform with the
ever beautiful colonial home. It is not difficult to build and
will keep in good shape for many years.

The dimensions and the manner of making the forms for the
concrete, and the location for the bolts to hold the plate and
rafters, are shown in the diagram.

Contributed by Edith E. Lane, El Paso, Texas.

Nutshell Photograph Novelty

Photograph in the Shell

Split an English walnut in the center, remove the contents, and
scrape out the rough parts. Make an oval opening by filing or
grinding. If a file is used, it should be new and sharp. After
this is done, take a small half round file and smooth the edges
into shape and good form.

The photograph print should be quite small—less than 1/2 in.
across the face. Trim the print to a size a little larger than
the opening in the shell, and secure it in place with glue or
paste. It may be well to fill the shell with cotton. Mount the
shell on a small card with glue, or if desired, a mount of
different shape can be made of burnt woodwork.

Contributed by C. S. Bourne, Lowell, Mass.

Spoon Holder on a Kettle

Spoon Holder

In making marmalade and jellies the ingredients must be stirred
from time to time as the cooking proceeds. After stirring, some
of the mixture always remains on the spoon. Cooks often lay the
spoon on a plate or stand it against the cooking utensil with the
handle down. Both of these methods are wasteful. The accompanying
illustration shows a device made of sheet copper to hold the
spoon so that the drippings will return to the cooking utensil.
The copper is not hard to bend and it can be shaped so that the
device can be used on any pot or kettle.

Contributed by Edwin Marshall, Oak Park, Ill.

Repairing Cracked Gramophone Records

Some time ago I received two gramophone records that were cracked
in shipment but the parts were held together with the paper
label. As these were single-faced disk records, I used the
following method to stick them together: I covered the back of
one with shellac and laid the two back to back centering the
holes with the crack in one running at right angles to the crack
in the other. These were placed on a flat surface and a weight
set on them. After several hours’ drying, I cleaned the surplus
shellac out of the holes and played them.

As the needle passed over the cracks the noise was hardly
audible. These records have been played for a year and they sound
almost as good as new.

Contributed by Marion P. Wheeler, Greenleaf, Oregon.

New Use for a Vacuum Cleaner

An amateur mechanic who had been much annoyed by the insects
which were attracted to his electric lights found a solution in
the pneumatic moth trap described in a recent issue of Popular
Mechanics. He fixed a funnel to the end of the intake tube of a
vacuum cleaner and hung it under a globe. The insects came to the
light, circled over the funnel and disappeared. He captured
several pounds in a few hours.

Contributed by Geo. F. Turl, Canton, Ill.

Filtering with a Small Funnel

In filtering a large amount of solution one usually desires
some means other than a large funnel and something to make the
watching of the process unnecessary. If a considerable quantity
of a solution be placed in a large bottle or flask, and a cork
with a small hole in it inserted in the mouth, and the apparatus
suspended in an inverted position over a small funnel so that the
opening of the cork is just below the water level in the funnel,
the filtering process goes on continuously with no overflow of
the funnel.

As soon as the solution in the funnel is below the cork, air is
let into the flask and a small quantity of new solution is let
down into the funnel. The process works well and needs no
watching, and instead of the filtrate being in a large filter
paper, it is on one small piece and can be handled with ease.

Contributed by Loren Ward, Des Moines, Iowa.

A Postcard Rack

Finished Rack

Details of the Rack

The illustration shows a rack for postcards. Those having houses
with mission-style furniture can make such a rack of the same
material as the desk, table or room furnishings and finish it in
the same manner.

The dimensions are given in the detail sketch. The two ends are
cut from 1/4-in. material, the bottom being 3/8 in. thick. Only
three pieces are required, and as they are simple in design,
anyone can cut them out with a saw, plane and pocket knife.

Contributed by Wm. Rosenberg, Worcester, Mass.

Substitute Shoe Horn

A good substitute for a shoe horn is a handkerchief or any piece of
cloth used in the following way: Allow part of the handkerchief
or cloth to enter the shoe, place the toe of the foot in the shoe
so as to hold down the cloth, and by pulling up on the cloth so
as to keep it taut around the heel the foot will slide into the
shoe just as easily as if a shoe horn were used.

Contributed by Thomas E. Dobbins, Glenbrook, Conn.

Building a Small Photographic Dark Room

In building a photographic dark room, it is necessary to make it
perfectly light-tight, the best material to use being matched
boards. These boards are tongued and grooved and when put
together effectually prevent the entrance of light.

The next important thing to be considered is to make it
weather-tight, and as far as the sides are concerned the matched
boards will do this also, but it is necessary to cover the roof
with felt or water-proof paper.

The best thickness for the boards is 1 in., but for cheapness 3/4
in. will do as well, yet the saving is so little that the 1-in.
boards are preferable.

The dark room shown in the accompanying sketch measures 3 ft. 6
in. by 2 ft. 6 in., the height to the eaves being 6 ft. Form the
two sides shown in Fig 1, fixing the crosspieces which hold the
boards together in such positions that the bottom one will act as
a bearer for the floor, and the second one for the developing
bench. Both sides can be put together in this way, and both
exactly alike. Keep the ends of the crosspieces back from the
edges of the boards far enough to allow the end boards to fit in
against them.

One of the narrow sides can be formed in the same way, fixing the
crosspieces on to correspond, and then these three pieces can be
fastened together by screwing the two wide sides on the narrow
one.

Lay the floor next, screwing or nailing the boards to the
crosspieces, and making the last board come even with the ends of
the crosspieces, not even with the boards themselves. The single
boards can then be fixed, one on each side of what will be the
doorway, by screwing to the floor, and to the outside board of
the sides. At the top of the doorway, fix a narrow piece between
the side boards, thus leaving a rectangular opening for the door.

The roof boards may next be put on, nailing them to each other at
the ridge, and to the sides of the room at the outsides and
eaves. They should overhang at the sides and eaves about 2 in.,
as shown in Figs. 3 and 4.

One of the sides with the crosspieces in place will be as shown
in Fig. 2 in section, all the crosspieces and bearers
intersecting around the room.

The door is made of the same kind of boards held together with
crosspieces, one of which is fastened so as to fit closely to the
floor when the door is hinged, and act as a trap for the light.
The top crosspiece is also fastened within 1 in. of the top of
the door for the same reason.

Light traps are necessary at the sides and top of the door. That
at the hinged side can be as shown at A, Fig. 5, the closing side
as at B, and the top as at C in the same drawing. These are all
in section and are self-explanatory. In hinging the door, three
butt hinges should be used so as to keep the joint close.

The fittings of the room are as shown sectionally in Fig. 6, but
before fixing these it is best to line the room with heavy, brown
wrapping paper, as an additional safeguard against the entrance
of light.

The developing bench is 18 in. wide, and in the middle an
opening, 9 by 11 in., is cut, below which is fixed the sink. It
is shown in detail in Fig. 7, and should be zinc
lined.

The zinc should not be cut but folded as shown in Fig. 8, so that
it will fit inside the sink. The bench at each side of the sink
should be fluted (Fig. 9), so that the water will drain off into
the sink. A strip should be fixed along the back of the bench as
shown in Figs. 6 and 9, and an arrangement of slats (Fig. 10),
hinged to it, so as to drop on the sink as in Fig. 6, and shown
to a larger scale in Fig. 11.

Details of the Dark Room

A shelf for bottles and another for plates, etc., can be fixed
above the developing bench as at D and E (Fig. 6) and another as
F in the same drawing. This latter forms the bottom of the tray
rack, which is fixed on as shown in Fig. 13. The divisions of the
tray rack are best fitted loosely in grooves formed by fixing
strips to the shelves and under the bench and sink as in Fig. 13.

Extra bearing pieces will be wanted for the shelves mentioned
above, these being shown in Fig. 14. The window is formed by
cutting an opening in the side opposite the door, and fixing in
it a square of white glass with strips of wood on the inside and
putty on the outside, as in Fig. 15. A ruby glass is framed as
shown at G, Fig. 16, and arranged to slide to and fro in the
grooved runners H, which makes it possible to have white light,
as at I, or red light as at K, Fig. 16. The white glass with
runners in position is shown at L in the same drawing, but not
the red glass and frame. Ventilation is arranged for by boring a
series of holes near the floor, as at M, Fig. 6, and near the
roof as at N in the same drawing, and trapping the light without
stopping the passage of air, as shown in the sections, Fig. 17.

The finish of the roof at the gables is shown in Fig. 18, the
strip under the boards holding the felt in position when folded
under, and the same is true of the roll at the top of the roof in
Fig. 19.

The house will be much strengthened if strips, as shown in Fig.
20, are fastened in the corners inside, after lining with brown
paper, screwing them each way into the boards.

The door may have a latch or lock with a knob, but should in
addition have two buttons on the inside, fixed so as to pull it
shut tightly at top and bottom. A waste pipe should be attached
to the sink and arranged to discharge through the floor. A
cistern with pipe and tap can be fastened in the top of the dark
room, if desired, or the room may be made with a flat roof, and a
tank stand on it, though this is hardly advisable.

It is absolutely necessary that the room be well painted, four
coats at first is not too many, and one coat twice a year will
keep it in good condition.

A brick foundation should be laid so that no part of the room
touches the ground.

The Versatile Querl

Querl Made of Wood

“Querl” is the German name for a kitchen utensil which may be
used as an egg-beater, potato-masher or a lemon-squeezer. For
beating up an egg in a glass, mixing flour and water, or stirring
cocoa or chocolate, it is better than anything on the market.

This utensil is made of hardwood, preferably maple or ash. A
circular piece about 2 in. in diameter is cut from 1/2-in. stock
and shaped like a star as shown in Fig. 1, and a 3/8-in. hole
bored in the center for a handle. The handle should be at least
12 in. in length and fastened in the star as shown in Fig. 2.

In use, the star is placed in the dish containing the material to
be beaten or mixed and the handle is rapidly rolled between the
palms of the hands.

Contributed by W. Karl Hilbrich, Erie, Pennsylvania.

An Emergency Soldering Tool

Occasionally one finds a piece of soldering to do which is
impossible to reach with even the smallest of the ordinary
soldering irons or coppers. If a length of copper wire as large
as the job will permit and sufficiently long to admit being bent
at one end to form a rough handle, and filed or dressed to a
point on the other, is heated and tinned exactly as a regular
copper should be, the work will cause no trouble on account of
inaccessibility.

Contributed by E. G. Smith, Eureka Springs, Ark.

Smoothing Paper after Erasing

Collar Button Ends In Wood Stick

When an ink line is erased the roughened surface of the paper
should be smoothed or polished so as to prevent the succeeding
lines of ink from spreading. A convenient desk accessory for this
purpose can be made of a short piece of hardwood and two bone
collar buttons.

File off the head of one button at A and the base from another at
B. Bore a small hole D and E in each end of the wood handle C and
fasten the button parts in the holes with glue or sealing wax.
The handle can be left the shape shown or tapered as desired. The
small end is used for smoothing small erasures and the other end
for larger surfaces.

A Cherry Seeder

Hairpin In Stick

An ordinary hairpin is driven part way into a small round piece
of wood, about 3/8 in. in diameter and 2 or 2-1/2 in. long, for a
handle, as shown in the sketch. The hairpin should be a very
small size. To operate, simply insert the wire loop into the
cherry where the stem has been pulled off and lift out the seed.

Contributed by L. L. Schweiger, Kansas City, Mo.

A Dovetail Joint

Shape of Tenon and Mortise

The illustration shows an unusual dovetail joint, which, when put
together properly is a puzzle. The tenon or tongue of the joint
is sloping on three surfaces and the mortise is cut sloping to
match. The bottom surface of the mortise is the same width at
both ends, the top being tapering toward the base of the tongue.

Contributed by Wm. D. Mitchell, Yonkers, New York.

Base for Round-End Bottles

Base Made of Corks

The many forms of round-bottomed glass bottles used in chemical
laboratories require some special kind of support on which they
can be safely placed from time to time when the chemist does not,
for the moment, need them. These supports should not be made of
any hard material nor should they be good conductors of heat, as
such qualities would result in frequent breakage.

A French magazine suggests making the supports from the large
corks of glass jars in which crystal chemicals are usually
supplied from the dealers. The manner of making them is clearly
shown in the sketch. Each cork is cut as in Fig. 1 and placed on
a wire ring (Fig. 2) whose ends are twisted together and the last
section of cork is cut through from the inner side to the center
and thus fitted over the wire covering the twisted ends, which
binds them together. The corks in use are shown in Fig. 3.

Rustic Window Boxes

Artistic Flower Boxes

Instead of using an ordinary green-painted window box, why not
make an artistic one in which the color does not clash with the
plants contained in it but rather harmonizes with them.

Such a window box can be made by anyone having usual mechanical
ability, and will furnish more opportunities for artistic and
original design than many other articles of more complicated
construction.

The box proper should be made a little shorter than the length of
the window to allow for the extra space taken up in trimming and
should be nearly equal in width to the sill, as shown in Fig. 1.
If the sill is inclined, as is usually the case, the box will
require a greater height in front, to make it set level, as shown
in Fig. 2.

The box should be well nailed or screwed together and should then
be painted all over to make it more durable. A number of 1/2-in.
holes should be drilled in the bottom, to allow the excess water
to run out and thus prevent rotting of the plants and box.

Having completed the bare box, it may be trimmed to suit the
fancy of the maker. The design shown in Fig. 1 is very simple and
easy to construct, but may be replaced with a panel or other
design. One form of panel design is shown in Fig. 3.

Trimming having too rough a surface will be found unsuitable for
this work as it is difficult to fasten and cannot be split as
well as smooth trimming. It should be cut the proper length
before being split and should be fastened with brads. The
half-round hoops of barrels will be found very useful in
trimming, especially for filling-in purposes, and by using them
the operation of splitting is avoided. After the box is trimmed,
the rustic work should be varnished, in order to thoroughly
preserve it, as well as improve its appearance.

Antidote for Squirrel Pest

To the owner of a garden in a town where squirrels are protected
by law, life in the summer time is a vexation. First the
squirrels dig up the sweet corn and two or three replantings are
necessary. When the corn is within two or three days of being
suitable for cooking, the squirrels come in droves from far and
near. They eat all they can and carry away the rest. When the
corn is gone cucumbers, cabbages, etc., share the same fate,
being partly eaten into. At the risk of being arrested for
killing the squirrels I have used a small target rifle morning
and night, but during my absence the devastation went on
steadily. Last year they destroyed my entire corn crop. Traps do
no good; can’t use poison, too dangerous. But I have solved the
difficulty; it’s easy.

Shake cayenne pepper over the various vegetables which are being
ruined, and observe results.

Homemade Electric Stove
By J. F. Tholl

Pattern for Parts of the Electric Stove

The construction of an electric stove is very simple, and it can
be made by any home mechanic having a vise and hand drill. The
body is made of sheet or galvanized iron, cut out and drilled as
shown in Fig. 1.

Each long projection represents a leg, which is bent at right
angles on the center line by placing the metal in the jaws of a
vise and hammering the metal over flat. If just the rim is
gripped in the vise, it will give a rounding form to the lower
part of the legs. The small projections are bent in to form a
support for the bottom.

The bottom consists of a square piece of metal, as shown in Fig.
2. Holes are drilled near the edges for stove bolts to fasten it
to the bottom projections. Two of the larger holes are used for
the ends of the coiled rod and the other two for the heating-wire
terminals. The latter holes should be well insulated with
porcelain or mica. The top consists of a square piece of metal
drilled as shown in Fig. 3. Four small ears are turned down to
hold the top in place.

One end of the coiled rod is shown in Fig. 4. This illustrates
how two pins are inserted in holes, drilled at right angles, to
hold the coil on the bottom plate. The coiled rod is 3/16 in. in
diameter and 27 in. long. The rod is wrapped with sheet
asbestos, cut in 1/2-in. strips.

The length of the heating wire must be determined by a test. This
wire can be purchased from electrical stores. Stovepipe wire will
answer the purpose when regular heating wire cannot be obtained.
The wire is coiled around the
asbestos-covered rod, so that no
coil will be in contact with another coil. If, by trial, the coil
does not heat sufficiently, cut some of it off and try again.
About 9-1/2 ft. of No. 26 gauge heating wire will be about right.
The connection to an electric-lamp socket is made with ordinary
flexible cord, to which is attached a screw plug for making
connections.

Glass-Cleaning Solution

Glass tumblers, tubing and fancy bottles are hard to clean by
washing them in the ordinary way, as the parts are hard to reach
with the fingers or a brush. The following solution makes an
excellent cleaner that will remove dirt and grease from crevices
and sharp corners. To 9 parts of water add 1 part of strong
sulphuric acid.
The acid should be added to the water slowly and
not the water to the acid. Add as much bichromate of potash as
the solution will dissolve. More bichromate of potash should be
added as the precipitate is used in cleaning.

The chemicals can be purchased cheaply from a local drug store,
and made up and kept in large bottles. The solution can be used
over and over again.

Contributed by Loren Ward Des Moines, Iowa.

Automatic-Closing Kennel Door

Diagram of Closing Door

When the neighborhood cats are retired for the night and there is
nothing more to chase, my fox terrier seems to realize that his
usefulness for the day is over and begs to be put in his kennel
that he may not bark at the moon as some dogs are apt to do. This
necessitates my putting him out at a time when it may not be
convenient. Frequently in stormy weather this is a disagreeable
duty and I found a way to obviate it by making a trapdoor device
for his kennel as shown in the sketch whereby he may lock himself
in when he crosses the threshold.

The outer half A of the hinged trapdoor is made heavier than the
inner half B by a cleat, C, and a strip, D, to cause the door to
swing shut. The tripper stick E is set between cleats C and F to
hold the door open. When the dog steps on the inner half of the
trapdoor B, it falls to stop G, releasing tripper stick E (which
is heavier on the top end H) to cause it to fall clear of the
path of the trapdoor. The door then swings shut in the direction
of the arrow, the latch I engaging a slot in the door as it
closes, and the dog has locked himself in for the night. The
latch I is made of an old-fashioned gate latch which is mortised
in the bottom joist of the kennel. When releasing the dog in the
morning the door is set for the evening.

Contributed by Victor Labadie, Dallas, Texas.

Polishing Cloths for Silver

Mix 2 lb. of whiting and 1/2 oz. of oleic acid with 1 gal. of
gasoline. Stir and mix thoroughly. Soak pieces of gray outing
flannel of the desired size—15 by 12 in. is a good size—in this
compound. Wring the surplus fluid out and hang them up to dry,
being careful to keep them away from the fire or an open flame.
These cloths will speedily clean silver or plated ware and will
not soil the hands.

In cleaning silver, it is best to wash it first in hot water and
white soap and then use the polishing cloths. The cloths can be
used until they are worn to shreds. Do not wash them. Knives,
forks, spoons and other small pieces of silver will keep bright
and free from tarnish if they are slipped into cases made from
the gray outing flannel and treated with the compound. Separate
bags for such pieces as the teapot, coffee pot, hot-water pot,
cake basket and other large pieces of silverware will keep them
bright and shining.

Contributed by Katharine D. Morse, Syracuse, N. Y.

A Book-Holder

Fig 2. Box Corner Makes a Book Holder

Books having a flexible back are difficult to hold in an upright
position when copying from them. A makeshift combination of
paperweights and other books is often used, but with
unsatisfactory results.

The book-holder shown in the sketch will hold such books
securely, allow the pages to be turned easily and conceal the
smallest possible portion of each page.

The holder can be cut out of a box corner and fitted with two
screw eyes, which have the part shown by the dotted lines at A
(Fig. 1) removed. The length of the back board determines the
slope for the book rest.

Contributed by James M. Kane, Doylestown, Pa.

Clamping a Cork

It is aggravating to continually break the cork of the stock
mucilage bottle because of its sticking to the neck of the bottle
after a supply has been poured out. If a stove bolt is inserted
lengthwise through the cork with a washer on each end and the nut
screwed up tightly, as shown in the sketch, the cork may be made
to last longer than the supply of mucilage and can be placed in a
new bottle and used over and over again.

Withdrawing Paper from under an Inverted Bottle

Invert a bottle on a piece of paper near the edge of a table top
and ask anyone to remove the paper without overturning the
bottle. They will at once jerk the paper with the result that the
bottle will turn over. To remove the paper just strike the table
top with your right fist while pulling the paper slowly with your
left hand. As you strike the table the bottle will jump and
release the paper.

Contributed by Maurice Baudier, New Orleans, La.

Emergency Tire Repair

A bone collar button makes a good substitute for a plug in
repairing a puncture in a single-tube bicycle tire.

Broom Holder Made of a Hinge

The broom holder shown in the sketch is made of an ordinary hinge
with one wing screwed to the wall. The loose wing has a large
hole drilled in it to receive the handle of the broom. The manner
of holding the broom is plainly shown in the sketch.

Contributed by Theodore L. Fisher; Waverly, Ill.

Making Proofs before the Negative Dries

A correspondent of Camera Craft makes proofs from his developed,
but unfixed, negatives, by squeezing a sheet of wet bromide paper
into contact with the wet film and giving an exposure several
times longer than would be required under ordinary conditions,
using the paper dry. If the developer is well rinsed out of the
film, the exposure to artificial light necessary to make a print
will have no injurious effect upon the negative, which is, of
course, later fixed and washed as usual.

Flower-Pot Stand

A very useful stand for flower pots can be made of a piece of
board supported by four clothes hooks. The top may be of any size
suitable for the flower pot. The hooks which serve as legs are
fastened to the under side of the board in the same manner as
fastening the hook to a wall.

Contributed by Oliver S. Sprout, Harrisburg, Pa.

A Line Harmonograph

As an apparatus capable of exciting interest, probably nothing so
easily constructed surpasses the harmonograph. Your attention
will be completely absorbed in the ever changing, graceful sweep
of the long pendulum, the gyrations of which are faithfully
recorded in the resulting harmonogram.

A careless impetus given to the pendulum may result in a very
beautiful harmonogram, but you may try innumerable times to
duplicate this chance record without success. No two hamonograms
are exactly alike. The harmonograph, while its pendulum swings in
accordance with well known natural laws, is exceedingly erratic
when it comes to obeying any preconceived calculations of its
operator. In this uncertainty lies the charm. If time hangs
heavily or a person is slightly nervous or uneasy, a harmonograph
is a good prescription.

The prime essential in a well working harmonograph is a properly
constructed universal joint. Where such a joint is made with
pivots for its bearings, one pair of pivots are very liable to
have more friction than the other, which retards the movement and
causes the harmonograph to undergo a continuous change of axis.
To obviate this difficulty, the joint should be made similar to
those used on scales. The general appearance of such a joint is
shown in the first illustration, Fig. 1. Stirrups A and B are
made of 7/8 by 1/4-in. metal. Holes are drilled in each end of
these stirrups and filed out as shown at C. The two holes shown
in the center of the stirrup A are drilled to fasten the
apparatus to the ceiling. Two corresponding holes are drilled in
B to fasten the long pendulum F to the joint. The cross of the
joint D has the ends shaped as shown at E. The rounded shoulder
on E is to prevent the cross from becoming displaced by a jar or
accident. The ends of the cross are inserted through the holes C
of the stirrups, then slipped back so the knife edges engage in
the V-shaped holes of the stirrups. The cross must be so made
that the knife edges will be in the same plane. This can be
determined by placing two of the knife edges on the jaws of a
vise and then laying two rules across the other two edges. The
rules should just touch the jaws of the vise and the two knife
edges of the cross. This makes a universal joint almost free from
friction and, what is most important, prevents the pendulum from
twisting on its own axis.

The pendulum F should be made of ash or oak, 1-3/4 by 2 in., with
a length depending on the height of the ceiling. A length of 7
ft. is about right for a 10-ft. ceiling.

A small table or platform, K, as shown in the lower part of Fig.
1, is fastened to the lower end of the pendulum as a support for
the cards on which harmonograms are made. A weight, G, of about
30 or 40 lb.-a box filled with small weights will do—is attached
to the pendulum just above the table. Another weight of about 10
lb. is attached as shown at H. A pedestal, J, provides a means of
support for the stylus. The stylus arm should have pin-point
bearings, to prevent any side motion.

The length of the short pendulum H, which can be regulated, as
shown in Fig. 1, should bear a certain and exactly fixed relation
to the length of the main pendulum, for the swinging times of
pendulums are inversely proportionate to their lengths, and
unless the shorter pendulum is, for instance, exactly one-third,
one-fourth, one-fifth, etc., as long as the other, that is, makes
respectively 3, 4 or 5 swings to one swing of the long pendulum,
they will not harmonize and a perfect harmonogram is not
obtained.

Lines Made with the Harmonograph

A good stylus to contain the ink is easily made from a glass tube
1/4 in. in diameter. Heat the tube in an alcohol or Bunsen flame
and then, by drawing the two portions apart and twisting at the
same time, the tube may be drawn to a sharp point. An opening of
any desired size is made in the point by rubbing it on a
whetstone. Owing to the fact that the style of universal joint
described has so little friction, the stylus point must be very
fine, or the lines will overlap and blur. A small weight, such as
a shoe buttoner, placed on the arm near the stylus will cause
enough friction to make the pendulum “die” faster and thus remedy
the trouble.

Contributed by Wm. R. Ingham, Rosemont, Arizona.

Cutting Circular Holes in Thin Sheet Metal

In arts and crafts work, occasion often arises to cut a perfectly
circular hole in sheet copper or brass. To saw and file it out
takes time and skill. Holes up to 3 in. in diameter can be cut
quickly and accurately with an ordinary expansive bit.

Fasten the sheet metal to a block of wood with handscrews or a
vise. Punch a hole, with a nail set or punch, in the center of
the circle to be cut, large enough to receive the spur of the
expansive bit. A few turns of the brace will cut out the circle
and leave a smooth edge.

Contributed by James T. Gaffney, Chicago.

Key Card for Writing Unreadable Post Cards

The Key Card

A key card for use in correspondence on postals that makes the
matter unreadable unless the recipient has a duplicate key card
is made as follows: Rule two cards the size of postal, one for
the sender and one for the receiver, dividing them into quarters.
These quarters are subsequently divided into any convenient
number of rectangular parts-six in this case.

These parts are numbered from one to six in each quarter
beginning at the outside corners and following in the same order
in each quarter. Cut out one rectangle of each number with a
sharp knife, distributing them over the whole card. Then put a
prominent figure 1 at the top of one side, 2 at the bottom and 3
and 4 on the other side. The numbering and the cutouts are
shown in Fig. 1. The two key cards are made alike.

The key card is used by placing it over a postal with the figure
1 at the top and writing in the spaces from left to right as
usual, Fig. 3, then put 2 at the top, Fig. 4, and proceed as
before, then 3 as in Fig. 5, and 4 as in Fig. 6. The result will
be a jumble of words as shown in Fig. 2, which cannot be read to
make any sense except by use of a key card.

Contributed by W.J. Morey, Chicago.

Homemade Carpenter’s Vise

The sketch shows an easily made, quick-working wood vise that has
proved very satisfactory. The usual screw is replaced by an open
bar held on one end by a wedge-shaped block, and the excess
taken up on the other end by an eccentric lever. The wedge is
worked by a string passing through the top of the bench and
should be weighted on the other end to facilitate the automatic
downward movement. The capacity of the vise, of course, depends
on the size and shape of the wedge-shaped block.

Contributed by J.H. Cruger, Cape May City, N.J.

Toning Blue on Bromide and Platinum

After some experimenting to secure a blue tone on bromide prints,
a correspondent of the Photographic Times produced a very
pleasing bluish green tint by immersing the prints in a solution
composed of 30 gr. of ferricyanide of potash,
30 gr. citrate of
iron and ammonia, 1/2 oz. acetic acid and 4 oz. of water. After
securing the tint desired, remove the prints, rinse them in clean
water for a few minutes, and then place them in a dilute solution
of hydrochloric acid.
Wash the prints thoroughly and hang them up with clips to dry.

Cutting Loaf Bread

When cutting a loaf of bread do not slice it from the outer
crusted end. Cut through the center, then cut slices from the
center toward the ends. The two cut surfaces can be placed
together, thus excluding the air and keeping the bread fresh as
long as there is any left to slice.

Contributed by L. Alberta Norrell, Augusta, Ga.

How to Make an Electric Toaster

Detail of Toaster

Toaster Complete

The electric toaster shown in the sketch is not hard to make. The
framework comprising the base and the two uprights may be made
either of hardwood or asbestos board,
says Popular Electricity.
If constructed of the former, the portion of the base under the
coil, and the inside surfaces of the two uprights should be
covered with a 1/8-in. sheet of well made
asbestos paper, or thin
asbestos board may be substituted for this lining.
Asbestos board
is to be preferred, and this material in almost any degree of
hardness may be purchased. It can be worked into shape and will
hold wood screws. The detail drawing gives all dimensions
necessary to shape the wood or asbestos board.

After preparing the base and uprights, drill 15 holes, 1/4 in.
deep, into the inside face of each upright to support the No. 6
gauge wires shown. The wires at the top and bottom for holding
the resistance wire are covered with
asbestos paper and the holes
for these wires are 3/4 in. from the top and bottom,
respectively, of the uprights. The wires that form the cage about
the heater coil and are used for a support for the toast are 15
pieces of No. 6 gauge iron wire each 8 in. long. The screws that
hold the uprights in position should have the heads countersunk
on the under side of the base. The binding-posts should now be
set in position and their protecting covering containing the
reinforced cord left until the other parts are finished.

To assemble, secure one upright in position using 1-1/2 in.
wood-screws. Place the other upright where it belongs without
fastening it and put the stretcher wires for holding the
resistance wire in place. Put the
asbestos paper on these and
with the assistance of a helper begin winding on the heater coil.
Use 80 ft. of 18-per-cent No. 22 gauge German-silver wire. Wind
the successive turns of wire so they will not touch each other
and fasten at each end with a turn or two of No. 16 gauge copper
wire. When this is complete have the helper hold the stretcher
wires while you tip the unfastened upright out and insert the
wires of the cage, then fasten the upright in place.

The wire from the binding-posts to the coil may be what is known
underwriters’ wire or
asbestos-covered wire No. 14 gauge, which
is held in place by double-headed tacks containing an insulation
at the head. These may be procured from electrical supply
houses. Connect the reinforced cord and terminals to the binding
screws and fasten the cover in place. This toaster will take four
amperes on [a] 110-volt circuit.

Cabinet for the Amateur’s Workshop

Empty Cigar Boxes Used for Drawers

One of the most convenient adjuncts to an amateur’s workbench is
a cabinet of some sort in which to keep nails, rivets, screws,
etc., instead of leaving them scattered all about the bench. A
very easily made cabinet for this purpose is shown in the
accompanying illustration. The case may be made of 1/2-in. white
pine or white wood of a suitable size to hold the required number
of drawers which slide on strips of the same material, cut and
dressed 1/2 in. square. The drawers are made of empty cigar boxes
of uniform size, which, if one is not a smoker, may be readily
obtained from any cigar dealer, as they are usually thrown away
when empty.

Small knobs may be added if desired, but these are not necessary,
as the spaces shown between the drawers give ample room to grasp
them with the fingers. Labels of some kind are needed, and one of
the neatest things for this purpose is the embossed aluminum
label, such as is stamped by the well known penny-in-the-slot
machines to be found in many railroad stations and amusement
places.

Contributed by Frederick E. Ward, Ampere, N. Y.

Uncurling Photographs

Photograph prints can be kept from curling when dry, by giving
them the same treatment as was once used on films. Immerse for 5
minutes in a bath made by adding 1/4 oz. of glycerine to 16 oz. of
water.

Soldering for the Amateur

Successful soldering will present no serious difficulties to
anyone who will follow a few simple directions. Certain metals
are easier to join with solder than others and some cannot be
soldered at all. Copper, brass, zinc, tin,
lead, galvanized iron,
gold and silver or any combination of these metals can be easily
soldered, while iron and aluminum are common metals that cannot
be soldered.

It is necessary to possess a soldering copper, a piece of solder,
tinner’s acid, sandpaper or steel wool, a small file and a piece
of sal ammoniac. If the soldering copper is an old one, or has
become corroded, it must be ground or filed to a point. Heat it
until hot (not red hot), melt a little solder on the sal
ammoniac, and rub the point of the copper on it, turning the
copper over to thoroughly tin the point on each face. This
process is known as tinning the iron and is very necessary to
successful work.

After the copper is tinned you may place it in the fire again,
being careful about the heat, as too hot an iron will burn off
the tinning.

The parts to be soldered must be thoroughly cleaned by
sandpapering or the use of steel wool until the metal shows up
bright. Then apply the acid only to the parts to be soldered with
a small stiff brush or a small piece of cloth fastened to a
stick, or in a bent piece of tin to form a swab.

Tinner’s acid is made by putting as much zinc in commercial
muriatic acid as will dissolve.
This process is best accomplished
in an open earthenware dish. After the acid has ceased to boil
and becomes cool it may be poured into a wide-mouthed bottle
which has a good top or stopper, and labeled “Poison.”

Place the parts to be soldered in their correct position and
apply the hot copper to the solder, then to the joint to be
soldered, following around with the copper and applying solder as
is necessary.

In joining large pieces it is best to “stick” them together in
several places to hold the work before trying to get all around
them. A little practice will soon teach the requisite amount of
solder and the smoothness required for a good job.

In soldering galvanized iron, the pure muriatic acid should be
used, particularly so when the iron has once been used.

C. G. S., Eureka Springs, Ark.

Washboard Holder

Clip on the Washboard

When using a washboard it will continually slip down in the tub.
This is considerable annoyance, especially if a large tub is
used. The washboard can be kept in place with small metal hooks,
as shown in the sketch. Two of these are fastened to the back of
the washboard in the right place to keep it at the proper slant.

Contributed by W. A. Jaquythe, Richmond, California.

A Mission Bracket Shelf

Details of the Wall Bracket

The shelf consists of six pieces of wood A, B, C, D, E and F. The
material can be of any wood. I have one made of mahogany finished
in natural color, and one made of poplar finished black. The
dimensions given in the detail drawings are sufficient for anyone
to make this bracket. The amount of material required is very
small and can be made from scrap, or purchased from a mill
surfaced and sanded. The parts are put together with dowel pins.

Contributed by A. Larson, Kenosha, Wis.

How to Make a Finger Ring

Tools for Forming the Ring

While the wearing of copper rings for rheumatism may be a foolish
notion, yet there is a certain galvanic action set up by the
contact of the acid in the system of the afflicted person with
the metal of the ring. Apart from this, however, a ring may be
made from any metal, such as copper, brass and silver, if such
metals are in plate or sheet form, by the following method:

All the tools necessary are a die and punch which are simple to
make and will form a ring that will fit the average finger. Take
a 3/4-in. nut, B, Fig. 1, and drill out the threads. This will
leave a clear hole, 7/8 in. in diameter, or a hole drilled the
desired size in a piece of iron plate will do as well.
Countersink the top of the hole so that the full diameter of the
countersink will be 1-1/4 in. This completes the die. The punch
A, is made of a piece of 5/8 in. round iron, slightly rounded on
the end so that it will not cut through the metal disk. The
dimensions shown in Fig. 1 can be changed to suit the size of the
finger to be fitted.
{40}
The metal used should be about 1/16 in. thick and 1-1/4 in. in
diameter. Anneal it properly by heating and plunging in water.
Lay it on the die so that it will fit nicely in the countersink
and drive it through the hole by striking the punch with a
hammer. Hold the punch as nearly central as possible when
starting to drive the metal through the hole. The disk will come
out pan shaped, C, and it is only necessary to remove the bottom
of the pan to have a band which will leave a hole 5/8 in. in
diameter and 1-1/4 in. wide. Place the band, D, Fig. 2, on a
stick so that the edges can be filed and rounded to shape. Finish
with fine emery cloth and polish. Brass rings can be plated when
finished.

Contributed by H. W. Hankin, Troy, N. Y.

How to Bind Magazines

A great many readers of Popular Mechanics Magazine save their
copies and have them bound in book form and some keep them
without binding. The bound volumes make an attractive library and
will always be valuable works of reference along mechanical
lines. I bind my magazines at home evenings, with good results.
Six issues make a well proportioned book, which gives two bound
volumes each year.

The covers of the magazines are removed, the wire binders pulled
out with a pair of pliers and the advertising pages removed from
both sides, after which it will be found that the remainder is in
sections, each section containing four double leaves or sixteen
pages. These sections are each removed in turn from the others,
using a pocket knife to separate them if they stick, and each
section is placed as they were in the magazine upon each
preceding one until all six numbers have been prepared. If
started with the January or the July issue, the pages will be
numbered consecutively through the entire pages of the six
issues.

Frame For Sewing Sections

The sections are then prepared for sewing. They are evened up on
the edges by jarring on a flat surface. They are then placed
between two pieces of board and all clamped in a vise. Five cuts,
1/8 in. deep, are made with a saw across the back of the
sections, as shown in Fig. 1. Heavy plain paper is used for the
flyleaves. The paper is cut double the same as the leaves
comprising the sections, making either one or two double sections
for each side as desired.

A frame for sewing will have to be made as shown in Fig. 2 before
the work can be continued on the book. The frame is easily made
of four pieces of wood. The bottom piece A should be a little
larger than the book. The two upright pieces B are nailed to the
outside edge, and a third piece, C, is nailed across the top.
Small nails are driven part way into the base C to correspond to
the saw cuts in the sections. A piece of soft fiber string is
stretched from each nail to the crosspiece C and tied.

Coarse white thread, size 16 or larger, is used for the sewing
material. Start with the front of the book. Be sure that all
sections are in their right places and that the flyleaves are
provided in the front and back. Take the sections of the
flyleaves on top, which should be notched the same as the saw
cuts in the book sections, and place them against the strings in
the frame. Place the left hand on the inside of the leaves where
they are folded and start a blunt needle, threaded double,
through the notch on the left side of the string No. 1 in Fig. 2.
Take hold of the needle with the right hand and pass it to the
left around the string No. 1, then back through the notch on the
right side. Fasten the thread by tying or making a knot in the
end and passing the needle through it. After drawing the thread
tightly, pass the needle through the notch on the left side of
the string No. 2, passing it around the string and tying in the
same manner as for No. 1.
{41}
Each section is fastened to the five
strings in the same manner, the thread being carried across from
each tie from No. 1 to 2 then to 3 and so on until all strings
are tied. The string No. 5 is treated in the same manner only
that the needle is run through on the left side of the string a
second time, leaving the needle on the outside in position for
the next section, which is fastened the same as the first, the
needle being passed through the notch on the right side of the
string No. 5, and then to string No.4, passing around on the
right side and back on the left and so on. Keep the thread drawn
up tightly all the time.

After the sewing is completed cut the strings, allowing about 2
in. of the ends extending on each side. The fibers of these ends
are separated and combed out so that they can be glued to the
covers to serve as a hinge. A piece of cheesecloth is cut to the
size of the back and glued to it. Ordinary liquid glue is the
best adhesive to use.

Procure heavy cardboard for the covers and cut two pieces 1/2 in.
longer and just the same width as the magazine pages. The
covering can be of cloth, leather or paper according to the taste
and resources of the maker. The covering should be cut out 1 in.
larger on all edges than both covers and space on the back. Place
the cardboard covers on the book, allowing a margin of 1/4 in. on
all edges except the back, and measure the distance between the
back edges of the covers across the back of the book.

Place the cardboard covers on the back of the covering the proper
distance apart as measured for the back, and mark around each
one. Spread a thin coat of glue on the surface of each and lay them
on by the marks made. Cut a notch out of the covering so it will
fold in, and, after gluing a strip of paper to the covering
between the covers to strengthen the back, fold over the outside
edges of the covering and glue it down all around.

The Bound Book

Place the cover on the book in the right position, glue the
hinges fast to the inside of the covers, then glue the first
flyleaf to the inside of the cover on both front and back and
place the whole under a weight until dry.

Contributed by Clyde E. Divine, College View, Nebr.

Metal Coverings for Leather Hinges

Metal Parts Screwed on Leather Hinge

A method of making a leather hinge work as well as an ordinary
steel butt is to cover the wings with sheet metal. The metal can
be fastened with nails or screws over the parts of the leather
attached to the wood. Tinplate, iron hoops, zinc or thin brass
cut in neat designs will make a leather hinge appear as well as a
metal hinge.

Contributed by Tom Hutchinson, Encanto, Cal.

Removing Plaster from Skin

A hot-water bottle held against a porous plaster will assist in
quickly removing it from the skin.

How to Make a Cheap Bracket Saw

Hacksaw Frame and Blade

For the frame use 3/8-in. round iron, bending it as shown in the
diagram and filing a knob on each end, at opposite sides to each
other, on which to hook the blade.

For the blade an old talking-machine spring or a clock spring
will do nicely. Heat the spring enough to take some of the temper
out of it, in order to drill the holes in the ends, as shown, and
file in the teeth. Make the blade 12 in. long, with 10 teeth to
the inch. A and B show how the blade fits on the frame.

Contributed by Willard J. Hays, Summitville, Ohio.

How to Make a Cannon

Toy Cannon

A cannon like the one in the cut may be made from a piece of
1-in. hydraulic pipe, A, with a steel sleeve, B, and a long
thread plug, C. Be sure to get hydraulic pipe, or double extra
heavy, as it is sometimes called, as common gas pipe is entirely
too light for this purpose. Don’t have the pipe too long or the
cannon will not make as much noise. Seven or eight inches is
about the right length for a 1-in. bore. Screw the plug and pipe
up tightly and then drill a 1/16-in. fuse hole at D.

If desired the cannon may be mounted on a block of wood, F, by
means of a U-bolt or large staple, E.

Contributed by Carson Birkhead, Moorhead, Miss.

Controller for a Small Motor

Reverse for Motor

An easy way of making a controlling and reversing device for
small motors is as follows:

Cut a piece of wood (A) about 6 in. by 4-1/2 in., and 1/4 in.
thick, and another piece (B) 6 in. by 1 in., and 1/4 in. thick.
Drive a nail through this near the center for a pivot (C). To the
under side of one end nail a copper brush (D) to extend out about
an inch. On the upper side, at the same end, nail another brush
(E) so that it projects at both sides and is bent down to the
level of the end brush. Then on the board put a semi-circle of
brass-headed tacks as shown at F, leaving a small space at the
middle and placing five tacks on either side, so that the end
brush will come in contact with each one. Connect these tacks on
the under side of the board with coils of German-silver wire,
using about 8 in. of wire to each coil. Fix these by soldering or
bending over the ends of the tacks. Then nail two strips of
copper (G) in such position that the side brush will remain on
the one as long as the end brush remains on the tacks on that
side.

Put sides about 1-1/2 in. high around this apparatus, raising the
board a little from the bottom to allow room for the coil. A lid
may be added if desired. Connect up as shown.

Contributed by Chas. H. Boyd, Philadelphia.

How to Make a Simple Water Rheostat

Wiring Plan for Water Rheostat

The materials necessary are: One 5-point wood-base switch, 4
jars, some sheet copper or brass for plates, about 5 ft. of
rubber-covered wire, and some No. 18 gauge wire for the wiring.

The size of the jars depends on the voltage. If you are going to
use a current of low tension, as from batteries, the jars need
not be very large, but if you intend to use the electric light
current of 110 voltage it will be necessary to use large jars or
wooden boxes made watertight, which will hold about 6 or 7 gal.
Each jar to be filled with 20 parts water to 1 part
sulphuric acid.
Jars are set in a row in some convenient place out of the
way.

Next cut out eight copper or brass disks, two for each jar. Their
size also depends on the voltage. The disks that are placed in
the lower part of the jars are connected with a rubber covered
wire extending a little above the top of the jar.

To wire the apparatus, refer to the sketch and you will see that
jar No. 1 is connected to point No. 1 on switch; No. 2, on No. 2,
and so on until all is complete and we have one remaining point
on switch. Above the jars place a wire to suspend the other or
top disks in the solution. This wire is also connected to one
terminal on the motor and to remaining point on switch. The arm
of the switch is connected to one terminal of battery, or source
of current, and the other terminal connected direct to remaining
terminal of motor.

Put arm of switch on point No. 1 and lower one of the top disks
in jar No. 1 and make contact with wire above jars. The current
then will flow through the motor. The speed for each point can be
determined by lowering top disks in jars. The top disk in jar No.
2 is lower down than in No. 1 and so on for No. 3 and No. 4. The
connection between point No. 5 on switch, direct to wire across
jars, gives full current and full speed.

How to Build a Toboggan Sled
By A. Boette

Construction a “Winner” Toboggan Sled

The first object of the builder of a sled should be to have a
“winner” both in speed and appearance. The accompanying
instructions for building a sled are designed to produce these
results.

The sled completed should be 15 ft. 2 in. long by 22 in. wide,
with the cushion about 15 in. above the ground. For the baseboard
select a pine board 15 ft. long, 11 in. wide and 2 in. thick, and
plane it on all edges. Fit up the baseboard with ten oak
foot-rests 22 in. long, 3 in. wide and 3/4 in. thick. Fasten them
on the under side of the baseboard at right angles to its length
and 16 in. apart, beginning at the rear. At the front 24 or 26
in. will be left without cross bars for fitting on the auto
front. On the upper side of the cross bars at their ends on each
side screw a piece of oak 1 in. square by 14 ft. long. On the
upper side of the baseboard at its edge on each side screw an oak
strip 3 in. wide by 3/4 in. thick and the length of the sled from
the back to the auto front. These are to keep the cushion from
falling out. See Fig. 1. For the back of the sled use the upper
part of a child’s high chair, taking out the spindles and
resetting them in the rear end of the baseboard. Cover up the
outside of the spindles with a piece of galvanized iron.

The construction of the runners is shown by Figs. 2 and 3. The
stock required for them is oak, two pieces 30 in. by 5 in. by
1-1/4 in., two pieces 34 in. by 5 in. by 1-1/4 in., two pieces 14
in. by 6 in. by 2 in., and four pieces 14 in. by 2 in. by 1 in.
They should be put together with large screws about 3 in. long.
Use no nails, as they are not substantial enough. In
proportioning them the points A, B and C, Fig. 2, are important.
For the front runners these measurements are: A, 30 in.; B, 4
in.; C, 15-1/2 in., and for the rear runners: A, 34 in.; B, 7 in.;
C, 16-1/2 in. The screw eyes indicated must be placed in a
straight line and the holes for them carefully centered. A
variation of 1/16 in. one way or another would cause a great deal
of trouble. For the steel runners use 3/8 in. cold-rolled steel
flattened at the ends for screw holes. Use no screws on the
running surface, however, as they “snatch” the ice.

The mechanism of the front steering gear is shown at Fig. 3. A
3/4-in. steel rod makes a good steering rod. Flatten the steering
rod at one end and sink it into the wood. Hold it in place by
means of an iron plate drilled to receive the rod and screwed to
block X. An iron washer, Z, is used to reduce friction; bevel
block K to give a rocker motion. Equip block X with screw eyes,
making them clear those in the front runner, and bolt through.
For the rear runner put a block with screw eyes on the baseboard
and run a bolt through.

Construct the auto front (Fig. 4) of 3/4-in. oak boards. The
illustration shows how to shape it. Bevel it toward all sides and
keep the edges sharp, as sharp edges are best suited for the
brass trimmings which are to be added. When the auto front is in
place enamel the sled either a dark maroon or a creamy white.
First sandpaper all the wood, then apply a coat of thin enamel.
Let stand for three days and apply another coat. Three coats of
enamel and one of thin varnish will make a fine-looking sled. For
the brass trimmings use No. 27 B. & S. sheet brass 1 in. wide on
all the front edges and pieces 3 in. square on the cross bars to
rest the feet against. On the door of the auto front put the
monogram of the owner or owners of the sled, cutting it out of
sheet brass.

For the steering-wheel procure an old freight-car “brake” wheel,
brass plated. Fasten a horn, such as used on automobiles, to the
wheel.

Make the cushion of leather and stuff it with hair. The best way
is to get some strong, cheap material, such as burlap, sew up one
end and make in the form of an oblong bag. Stuff this as tightly
as possible with hair. Then get some upholstery buttons, fasten a
cord through the loop, bring the cord through to the underside of
the cushion, and fasten the button by slipping a nail through the
knot. Then put a leather covering over the burlap, sewing it to
the burlap on the under side. Make the cushion for the back in
the same way. On top of the cushion supports run a brass tube to
serve the double purpose of holding the cushion down and
affording something to hold on to.

If desired, bicycle lamps may be fastened to the front end, to
improve the appearance, and it is well to have a light of some
kind at the back to avoid the danger of rear-end collisions.

The door of the auto front should be hinged and provided with a
lock so that skates, parcels, overshoes, lunch, etc. may be
stowed within. A silk pennant with a monogram adds to the
appearance.

If desired, a brake may be added to the sled. This can be a
wrought-iron lever 1-1/2 in. by 1/2 in. by 30 in. long, so
pivoted that moving the handle will cause the end to scrape the
ice. This sled can be made without lamps and horn at a cost of
about $15, or with these for $25, and the pleasure derived from
it well repays the builder. If the expense is greater than one
can afford, a number of boys may share in the ownership.

Burning Inscriptions on Trees

Scrape off the bark just enough to come to the first light under
coating, which is somewhat moist. With a lead pencil make an
outline of the inscription to be burnt on the tree and bring, the
rays of a large magnifying glass not quite to a fine focus on the
same. The tree will be burnt along the pencil marks, and if the
glass is not held in one spot too long, the inscription will be
burnt in as evenly as if it had been written.

Contributed by Stewart H. Leland, Lexington, Ill.

How to Make Small Gearwheels Without a Lathe

Making Model Wheels

To make small models sundry small gears and racks are required,
either cut for the place or by using the parts from an old clock.
With no other tools than a hacksaw, some files, a compass, and
with the exercise of a little patience and moderate skill, very
good teeth may be cut on blank wheels.

First take the case of a small gearwheel, say 1 in. outside
diameter and 1/16 in. thick, with twenty-four teeth. Draw a
circle on paper, the same diameter as the wheel. Divide the
circumference into the number of parts desired, by drawing
diameters, Fig. 1. The distance AB will be approximately the
pitch. Now describe a smaller circle for the base of the teeth
and halfway between these circles may be taken as the pitch
circle.

Now describe a circle the same size as the largest circle on a
piece of 1/16-in. sheet metal, and having cut it out and filed it
up to this circle, fasten the marked-out paper circle accurately
over it with glue. Saw-cuts can now be made down the diameters to
the smaller circle with the aid of a saw guide, Fig. 2, made from
1/16-in. mild steel or iron. This guide should have a beveled
edge, E, from F to G, to lay along the line on which the saw-cut
is to be made. The straight-edge, CD, should be set back one-half
the thickness of the saw-blades, so that the center of the blade,
when flat against it, will be over the line FG. A small clearance
space, FC, must be made to allow the teeth of the saw to pass.

The guide should then be placed along one of the diameters and
held in position until gripped in the vise, Fig. 3. The first
tooth may now be cut, care being taken to keep the blade of the
saw flat up to the guiding edge. The Model Engineer, London, says
if this is done and the saw-guide well made, the cut will be
central on the line, and if the marking-out is correct the teeth
will be quite uniform all the way round. A small ward file will
be needed to finish off the teeth to their proper shape and
thickness.

In making a worm wheel the cuts must be taken in a sloping
direction, the slope and pitch depending on the slope and pitch
of the worm thread, which, though more difficult, may also be cut
with a hacksaw and file.

A bevel wheel should be cut in the same manner as the spur wheel,
but the cut should be deeper on the side which has the larger
diameter. To cut a rack the pitch should be marked along the
side, and the guide and saw used as before (Fig. 4).

How to Make Four Pictures on One Plate

Four Photos on One Plate

Secure two extra slides for the plate holders and cut one corner
out on one of them, as shown in Fig. 1. Make a hole in the other,
as shown in Fig. 2. With a lead pencil draw on the ground glass
one line vertical and one horizontal, each in the center. This
will divide the ground glass into four equal parts.

Focus the camera in the usual manner, but get the picture desired
to fill only one of the parts on the ground glass. Place the
plate-holder in position and draw the regular slide; substitute
one of the slides prepared and expose in the usual way.

If a small picture is to be made in the lower left-hand corner of
the plate, place the prepared slide with the corner cut, as shown
in Fig. 1. The slide may be turned over for the upper left hand
corner and then changed for slide shown in Fig. 2 for the upper
and lower right-hand corners.

Electric Blue-Light Experiment

Take a jump-spark coil and connect it up with a battery and start
the vibrator. Then take one outlet wire, R, and connect to one
side of a 2-cp. electric lamp, and the other outlet wire, B, hold
in one hand, and press all fingers of the other hand on globe at
point A. A bright, blue light will come from the wires in the
lamp to the surface of the globe where the fingers touch. No
shock will be perceptible.

Interesting Electrical Experiment

A Unique Battery

The materials necessary for performing this experiment are:
Telephone receiver, transmitter, some wire and some carbons,
either the pencils for arc lamps, or ones taken from old dry
batteries will do.

Run a line from the inside of the house to the inside of some
other building and fasten it to one terminal of the receiver. To
the other terminal fasten another piece of wire and ground it on
the water faucet in the house. If there is no faucet in the
house, ground it with a large piece of zinc.

Fasten the other end to one terminal of the transmitter and from
the other terminal of the same run a wire into the ground. The
ground here should consist either of a large piece of carbon, or
several pieces bound tightly together.

If a person speak into the transmitter, one at the receiver can
hear what is said, even though there are no batteries in the
circuit. It is a well known fact that two telephone receivers
connected up in this way will transmit words between two persons,
for the voice vibrating the diaphragm causes an inductive current
to flow and the other receiver copies these vibrations. But in
this experiment, a transmitter which induces no current is used.
Do the carbon and the zinc and the moist earth form a battery?

Contributed by Wm. J. Slattery, Emsworth, Pa.

A Cheap Fire Alarm

Electric Fire Alarm

An electrical device for the barn that will give an alarm in case
of fire is shown in the accompanying diagram. A is a wooden
block, which is fastened under the loft at a gable end of the
barn; B is an iron weight attached to the string C, and this
string passes up through the barn to the roof, then over a hook
or pulley and across the barn, under the gable, and is fastened
to the opposite end of the barn.

D D are binding posts for electric wires. They have screw ends,
as shown, by which means they are fastened to the wooden block A.
They also hold the brass piece E and the strip of spring brass F
in place against the wooden block. G is a leather strap fastened
to the weight B and the spring F connected to the latter by a
small sink bolt.

At the house an electric bell is placed wherever convenient.
Several battery cells, of course, are also needed. Dry batteries
are most convenient. The battery cells and bell are connected in
the usual manner, and one wire from the bell and one from the
battery are strung to the barn and connected to the binding posts
D D.

If a fire occurs in the hay-mow the blaze will generally shoot
toward the gable soon after it starts, and will then burn the
string C, which allows the weight B to fall and pull the brass
spring against the iron piece E, which closes the circuit and
rings the bell in the house.

If desired, the string may be stretched back and forth under the
roof several times or drawn through any place that is in danger
of fire.

Contributed by Geo. B. Wrenn, Ashland, Ohio.

How to Make a Small Electric Furnace

Electric Furnace

Take a block of wood and shape into a core. One like a loaf of
bread, and about that size, serves admirably. Wrap a layer of
asbestos
around it and cover this with a thin layer of
plaster-of-paris. When the plaster is nearly dry wind a coil of
No. 36 wire around it, taking care that the wire does not touch
itself anywhere. Put another course of plaster-of-paris on this,
and again wind the wire around it. Continue the process of
alternate layers of plaster and wire until 500 ft. or more of the
latter has been used, leaving about 10 in. at each end for
terminals. Then set the whole core away to dry.

For a base use a pine board 10 in. by 12 in. by 1 in. Bore four
holes at one end for binding-posts, as indicated by E E. Connect
the holes in pairs by ordinary house fuse wire. At one side
secure two receptacles, B B, and one single post switch, C. Place
another switch at I and another binding-post at F. The oven is
now ready to be connected.

Withdraw the wooden core from the coils of wire and secure the
latter by bands of tin to the board. Connect the ends of the wire
to binding-posts E and F, as shown. From the other set of
binding-posts, E, run a No. 12 or No. 14 wire, connecting lamp
receptacles, B B, and switch, C, in parallel. Connect these three
to switch, D, in series with binding-post, F, the terminal of the
coil. Place 16-cp. lights in the receptacles and connect the
fuses with a 110-volt lighting circuit. The apparatus is now
ready for operation. Turn on switch, D, and the lamps, while C is
open. The coil will commence to become warm, soon drying out the
plaster-of-paris. To obtain more heat open one lamp, and to
obtain still more open the other and close switch C.

Contributed by Eugene Tuttles, Jr., Newark, Ohio.

How to Make an Ammeter

Complete Ammeter and Details

Every amateur mechanic who performs electrical experiments will
find use for an ammeter, and for the benefit of those who wish to
construct such an instrument the following description is given:
The operative principle of this instrument is the same as that of
a galvanometer, except that its working position is not confined
to the magnetic meridian. This is accomplished by making the
needle revolve in a vertical instead of a horizontal plane. The
only adjustment necessary is that of leveling, which is
accomplished by turning the thumbscrew shown at A, Fig. 1, until
the hand points to zero on the scale.

First make a support, Fig. 2, by bending a piece of sheet brass
to the shape indicated and tapping for the screws CC. These
should have hollow ends, as shown, for the purpose of receiving
the pivoted axle which supports the hand. The core, Fig. 3, is
made of iron. It is 1 in. long, 1/4 in. wide and 1/8 in. thick.
At a point a little above the center, drill a hole as shown at H,
and through this hole drive a piece of knitting-needle about 1/2
in. long, or long enough to reach between the two screws shown in
Fig. 2. The ends of this small axle should be ground pointed and
should turn easily in the cavities, as the sensitiveness of the
instrument depends on the ease with which this axle turns.

After assembling the core as shown in Fig. 4, it should be filed
a little at one end until it assumes the position indicated. The
pointer or hand, Fig. 5, is made of wire, aluminum being
preferable for this purpose, although copper or steel will do.
Make the wire 4-1/2 in. long and make a loop, D, 1/2 in. from the
lower end. Solder to the short end a piece of brass, E, of such
weight that it will exactly balance the weight of the hand. This
is slipped on the pivot, and the whole thing is again placed in
position in the support. If the pointer is correctly balanced it
should take the position shown in Fig. 1, but if it is not
exactly right a little filing will bring it near enough so that
it may be corrected by the adjusting-screw.

Next make a brass frame as shown in Fig. 6. This may be made of
wood, although brass is better, as the eddy currents set up in a
conductor surrounding a magnet tend to stop oscillation of the
magnet. (The core is magnetized when a current flows through the
instrument.) The brass frame is wound with magnet wire, the size
depending on the number of amperes to be measured. Mine is wound
with two layers of No. 14 wire, 10 turns to each layer, and is
about right for ordinary experimental purposes. The ends of the
wire are fastened to the binding posts B and C, Fig. 1.

A wooden box, D, is then made and provided with a glass front. A
piece of paper is pasted on a piece of wood, which is then
fastened in the box in such a position that the hand or pointer
will lie close to the paper scale. The box is 5-1/2 in. high, 4
in. wide and 1-3/4 in. deep, inside measurements. After
everything is assembled put a drop of solder on the loop at D,
Fig. 5, to prevent it turning on the axle.

To calibrate the instrument connect as shown in Fig. 7, where A
is the homemade ammeter; B, a standard ammeter; C, a variable
resistance, and D, a battery, consisting of three or more cells
connected in multiple. Throw in enough resistance to make the
standard instrument read 1 ohm [sic: ampere] and then put a mark
on the paper scale of the instrument to be calibrated. Continue
in this way with 2 amperes, 3 amperes, 4 amperes, etc., until the
scale is full. To make a voltmeter out of this instrument, wind
with plenty of No. 36 magnet wire instead of No. 14, or if it is
desired to make an instrument for measuring both volts and
amperes, use both windings and connect to two pairs of binding
posts.

Contributed by J.E. Dussault, Montreal.

How to Make a Three-Way Cock for Small Model-Work

In making models of machines it is often necessary to contrive
some method for a 3 or 4-way valve or cock. To make one, secure
a pet cock and drill and tap hole through, as shown in the cut.
If for 3-way, drill in only to the opening already through, but
if for a 4-way, drill through the entire case and valve. Be sure
to have valve B turned so as to drill at right angles to the
opening through it. After drilling, remove the valve, take off
the burr with a piece of emery paper and replace ready for work.

Easy Experiments with Electric-Light Circuit

Arc-Light Motor and Water Rheostat

An electric-light circuit will be found much less expensive than
batteries for performing electrical experiments. The sketch shows
how a small arc light and motor may be connected to the light
socket, A. The light is removed and a plug with wire connections
is put in its place. One wire runs to the switch, B, and the
other connects with the water rheostat, which is used for
reducing the current.

A tin can, C is filled nearly to the top with salt water, and a
metal rod, D, is passed through a piece of wood fastened at the
top of the can. When the metal rod is lowered the current
increases, and as it is withdrawn the current grows weaker. In
this way the desired amount of current can be obtained. By
connecting the motor, E, and the arc light, F, as shown, either
one may be operated by turning switch B to the corresponding
point. The arc light is easily made by fastening two electric
light carbons in a wooden frame like that shown. To start the
light, turn the current on strong and bring the points of the
carbons together; then separate slightly by twisting the upper
carbon and at the same time drawing it through the hole.

How to Make an Interrupter

Details of Interrupter

The Completed Instrument

The Wenult interrupter is an instrument much used on large coils
and is far more efficient than the usual form of vibrators. It
can also be used with success on small coils as well as large.
Although it is a costly instrument to purchase, it can be made
with practically no expense and the construction is very simple.

First procure a wide-mouthed bottle about 4 in. high, provided
with a rubber stopper. This stopper should be pierced, making two
holes about 1/4 in. in diameter.

From a sheet of lead 1/16 in.
in thickness cut a piece shaped
like A, Fig. 1. Common tea lead
folded several times will serve
the purpose. When in the bottle this
lead should be of such a
size that it will only reach half way around, as shown in B. To
insert the lead plate,
roll it up so it will pass through the
neck of the bottle, then smooth it out with a small stick until
it fits against the side, leaving the small strip at the top
projecting through the neck of the bottle. Bend this strip to one
side and fit in the stopper, as shown in C. A small binding-post
is fastened at the end of the strip.

Having fixed the lead
plate in position, next get a piece of
glass tube having a bore of about 1/32 of an inch in diameter. A
piece of an old thermometer tube will serve this purpose. Insert
this tube in the hole in the stopper farthest from the
lead
plate. Get a piece of wire that will fit the tube and about 6 in.
long, and fasten a small binding-post on one end and stick the
other into the tube. This wire should fit the hole in the tube so
it can be easily moved. In the hole nearest the
lead plate insert a small glass funnel.

The interrupter as it is when complete is shown at D, Fig. 1.
Having finished the interrupter, connect it with the
electric-light circuit as shown in Fig. 2. Fill the bottle with
water to about the line as shown in D, Fig. 1. Adjust the wire in
the small glass tube so that it projects about 1/8 in. Add
sulphuric acid until the water level rises about 1/16 in. Turn on
the current and press the button, B. If all adjustments are
correct, there will be a loud crackling noise from the
interrupter, a violet flame will appear at the end of the wire
and a hot spark will pass between the secondary terminals. If the
interrupter does not work at first, add more sulphuric acid
through the funnel and press the wire down a little more into the
liquid. A piece of wood, A, Fig. 2, should be inserted in
vibrator to prevent it from working.

Contributed by Harold L. Jones, Carthage, N. Y.

A Miniature “Pepper’s Ghost” Illusion

Construction of the “Pepper’s Ghost” Illusion

Probably many readers have seen a “Pepper’s Ghost” illusion at
some amusement place. As there shown, the audience is generally
seated in a dark room at the end of which there is a stage with
black hangings. One of the audience is invited onto the stage,
where he is placed in an upright open coffin. A white shroud is
thrown over his body, and his clothes and flesh gradually fade
away till nothing but his skeleton remains, which immediately
begins to dance a horrible rattling jig. The skeleton then fades
away and the man is restored again.

A simple explanation is given in the Model Engineer. Between the
audience and the coffin is a sheet of transparent glass, inclined
at an angle so as to reflect objects located behind the scenes,
but so clear as to be invisible to the audience and the man in
the coffin. At the beginning the stage is lighted only from
behind the glass. Hence the coffin and its occupant are seen
through the glass very plainly. The lights in front of the glass
(behind the scenes) are now raised very gradually as those behind
the glass are turned down, until it is dark there. The perfectly
black surface behind the glass now acts like the silver backing
for a mirror, and the object upon which the light is now
turned—in this case the skeleton—is reflected in the glass,
appearing to the audience as if really occupying the stage.

The model, which requires no special skill except that of
carpentry, is constructed as shown in the drawings.

The box containing the stage should be 14 in. by 7 in. by 7-1/2
in., inside dimensions. The box need not be made of particularly
good wood, as the entire interior, with the exception of the
glass, figures and lights, should be colored a dull black. This
can well be done by painting with a solution of lampblack in
turpentine. If everything is not black, especially the joints and
background near A, the illusion will be spoiled.

The glass should be the clearest possible, and must be thoroughly
cleansed. Its edges should nowhere be visible, and it should be
free from scratches and imperfections. The figure A should be a
doll about 4 in. high, dressed in brilliant, light-colored
garments. The skeleton is made of papier maché, and can be bought
at Japanese stores. It should preferably be one with arms
suspended by small spiral springs, giving a limp, loose-jointed
effect. The method of causing the skeleton to dance is shown in
the front view. The figure is hung from the neck by a blackened
stiff wire attached to the hammer wire of an electric bell, from
which the gong has been removed. When the bell works he will kick
against the rear wall, and wave his arms up and down, thus giving
as realistic a dance as anyone, could expect from a skeleton.

The lights, L and M, should be miniature electric lamps, which
can be run by three dry cells. They need to give a fairly strong
light, especially L, which should have a conical tin reflector to
increase its brilliancy and prevent its being reflected in the
glass.

Since the stage should be some distance from the audience, to aid
the illusion, the angle of the glass and the inclination of the
doll, A, has been so designed that if the stage is placed on a
mantle or other high shelf, the image of A will appear upright to
an observer sitting in a chair some distance away, within the
limits of an ordinary room. If it is desired to place the box
lower down, other angles for the image and glass may be found
necessary, but the proper tilt can be found readily by
experiment.

The electric connections are so simple that they are not shown in
the drawings. All that is necessary is a two-point switch, by
which either L or M can be placed in circuit with the battery,
and a press button in circuit with the bell and its cell. If a
gradual transformation is desired, a double-pointed rheostat
could be used, so that as one light dims the other increases in
brilliancy, by the insertion and removal of resistance coils.

With a clear glass and a dark room this model has proved to be
fully as bewildering as its prototype.

Experiment with Colored Electric Lamps

Two-Colored Hand

To many the following experiment may be much more easily
performed than explained: Place the hand or other object in the
light coming from two incandescent lamps, one red and one white,
placed about a foot apart, and allow the shadow to fall on a
white screen such as a table-cloth. Portions of the shadow will
then appear to be a bright green. A similar experiment consists
in first turning on the red light for about a minute and then
turning it off at the same time that the white one is turned on.
The entire screen will then appear to be a vivid green for about
one second, after which it assumes its normal color.

To Explode Powder with Electricity

A 1-in. hole was bored in the center of a 2-in. square block. Two
finishing nails were driven in, as shown in the sketch. These
were connected to terminals of an induction coil. After
everything was ready the powder was poured in the hole and a
board weighted with rocks placed over the block. When the button
is pressed or the circuit closed in some other way the discharge
occurs. The distance between the nail points—which must be
bright and clean—should be just enough to give a good, fat
spark.

Contributed by Geo. W. Fry, San Jose, Cal.

Simple Wireless System

Simple Wireless System

The illustrations will make plain a simple and inexpensive
apparatus for wireless telegraphy by which I have had no
difficulty in sending messages across 1-1/2 miles of water
surface. It is so simple that the cuts scarcely need explanation.
In Fig. 1 is seen the sending apparatus, consisting of a 40-cell
battery connected with two copper plates 36 by 36 by 1/8 in. The
plates are separated 6 in. by a piece of hard rubber at each end.

In Fig. 2 are seen duplicates of these insulated plates,
connected with an ordinary telephone receiver. With this receiver
I can hear distinctly the electric signals made by closing and
opening the Morse key in Fig. 1, and I believe that in a short
time I shall be able to perfect this system so as to send
wireless messages over long distances.

Contributed by Dudley H. Cohen, New York.

Stop Crawling Water Colors

To prevent water colors from crawling, add a few drops of ammonia
or lime water, or a solution of sal soda.

Small Electrical Hydrogen Generator

Hydrogen Generator

A small hydrogen
generator may be made from a fruit jar, A (see
sketch), with two tubes, B and C, soldered in the top. The plates
E can be made of tin or galvanized iron, and should be separated
about 1/8 in. by small pieces of wood. One of these plates is
connected to metal top, and the wire from the other passes
through the tube B, which is filled with melted rosin or wax, to
make it airtight. This wire connects to one side of a battery of
two cells, the other wire being soldered to the metal top of the
jar, as shown. The jar is partly filled with a very dilute
solution of sulphuric acid, about 1 part of acid to 20 of water.

When the current of electricity passes between the plates E,
hydrogen gas is generated,
which rises and passes through the
rubber hose D, into the receiver G. This is a wide-mouth bottle,
which is filled with water and inverted over a pan of water, F.

The gas bubbling up displaces the water and fills the bottle. If
the receiver is removed when half full of gas, the remaining
space will be filled with air, which will mix with the gas and
form an explosive mixture. If a lighted match is then held near
the mouth of the bottle a sharp report will be heard.

If the bottle is fitted with a cork containing two wires nearly
touching, and the apparatus connected with an induction coil, in
such a manner that a spark will be produced inside the bottle,
the explosion will blowout the cork or possibly break the bottle.
Caution should be used to avoid being struck by pieces of flying
glass if this experiment is tried, and under no condition should
a lighted match or spark be brought near the end of the rubber
hose D, as the presence of a little air in the generator will
make an explosive mixture which would probably break the jar.

Gasoline Burner for Model Work

Gasoline Burner

When making a small model traction engine or a locomotive the
question arises, “What shall the fuel be?” If you have decided to
use gasoline, then a suitable burner is necessary. A piece of
brass tubing about 3 in. in diameter and 6 in. long with caps
screwed on both ends and fitted with a filling plug and a bicycle
valve makes a good gasoline supply tank, says the Model Engineer,
London. The bicycle valve is used to give the tank an air
pressure which forces the gasoline to the burner.

The burner is made from a piece of brass tube, A, as is shown in
the illustration, 1/2 in. in diameter and 2-1/2 in. long, which
is plugged up at both ends, one end being drilled and reamed out
to 5/16 in. Three rows of holes 1/16 in. in diameter are drilled
in the brass tube. One row is drilled to come directly on top,
and the other two at about 45 degrees from the vertical. It is
then fitted to a sheet steel base, B, by means of the clips, C C,
Fig. 1. A piece of 1/8-in. copper pipe, P, is then coiled around
the brass tube, A, which forms the vaporizing coil. This coil
should have a diameter of only 1 in. One end of the copper tube
is bent around so it will point directly into the reamed-out hole
in the end of the brass tube, A. A nipple, N, is made by
drilling a 1/8-in. hole halfway through a piece of brass and
tapping to screw on the end of the 1/8-in. copper pipe. A
1/64-in. hole is then drilled through the remaining part of the
nipple. The other end of the copper tube is connected to the
supply tank. The distance between the nipple, N, and the ends of
the tube, A, should be only 5/16 of an inch. Fig. 2 shows the end
view.

A Homemade Telephone Receiver

A telephone receiver that will do good work may be built very
cheaply as follows: For the case use an ordinary 1/2-lb.
baking-powder box with a piece of heavy wire soldered on the
inside, 1-5/16 in. from the bottom. For the magnet use a piece of
round hardened steel about 3/8 in. in diameter and 1-1/4 in.
long. If desired, a piece of an old round file may be used for
the magnet core, which should be magnetized previous to
assembling, either by passing a current of electricity around it,
or by direct contact with another magnet. The steel core should
be wound with about 250 ft. of No. 36 insulated wire, the ends of
which should be soldered to a piece of lamp cord, passed through
a hole in the bottom of the can and knotted inside to prevent
pulling out.

A disk of thin sheet-iron, such as is used by photographers for
tintypes (Ferrotype), should be cut to the diameter of the can,
taking care not to bend the iron. The magnet should then be
placed in the bottom of the can in an upright position and enough
of a melted mixture of beeswax and resin poured in to hold it in
position.

While the wax is still in a plastic condition the magnet should
be located centrally and adjusted so that the end will be 1/16
in. or less below the level of the top of the copper ring. After
the wax has hardened the disk is slipped in and fastened tightly
by a ring of solder when the instrument is ready for use.

How to Bind Magazines

Process of Homemade Binding

An easy way to bind Popular Mechanics in volumes of six months
each is to arrange the magazines in order and tie them securely
both ways with a strong cord. It is well to put two or three
sheets of tough white paper, cut to the size of the pages, at the
front and back for fly leaves.

Clamp the whole in a vise or clamp with two strips of wood even
with the back edges of the magazines. With a sharp saw cut a slit
in the magazines and wood strips about 1/2 in. deep and slanting
as shown at A and B, Fig. 1. Take two strips of stout cloth,
about 8 or 10 in. long and as wide as the distance between the
bottoms of the sawed slits. Lay these over the back edge of the
pack and tie securely through the slits with a string
thread—wrapping and tying several times (C, Fig. 2).

If you have access to a printer’s paper knife, trim both ends and
the front edge; this makes a much nicer book, but if the paper
knife cannot be used, clamp the whole between two boards and saw
off the edges, boards and all, smoothly, with a fine saw.

Cut four pieces of cardboard, 1/4 in. longer and 1/4 in. narrower
than the magazines after they have been trimmed. Lay one piece of
the board on the book and under the cloth strips. Use ordinary
flour paste and paste the strips to the cardboard and then rub
paste all over the top of the strips and the board. Rub paste
over one side of another piece of board and put it on top of the
first board and strips, pressing down firmly so that the strips
are held securely between the two boards. Turn the book over and
do the same with the other two boards.

After the paste has dried a few minutes take a piece of strong
cloth, duck or linen, fold and cut it 1 in. larger all around
than the book, leaving the folded edge uncut. Rub paste over one
of the board backs and lay one end of the cloth on it, smoothing
and creasing as shown at A, Fig. 3. Turn the book over and paste
the other side. The back edges should have a good coat of paste
and a strip of paper the width of the thickness of the pack
pasted on before pasting the cloth to the second board back.

Cut off the corners and fold over the edges of the cloth, pasting
them down (Fig. 4). Rub paste on one side of a fly leaf and press
the back down on it. Turn the book over and paste a fly leaf to
the other back after the edges of the cloth have been folded
down. The backs must not be opened until the fly leaves are
thoroughly dry. Trim and tuck in the ends of the strip at the
back edge. When fixed this way your magazines make one of the
most valuable volumes you can possibly add to your library of
mechanical books.

Contributed by Joseph N. Parker, Bedford City, Va.

A Homemade Acetylene-Gas Generator

A simple acetylene-gas
generator used by myself for several years
when out on camping trips was made of a galvanized iron tank,
without a head, 18 in. in diameter and 30 in. deep, B, as shown
in the sketch. Another tank, A, is made the same depth as B, but
its diameter is a little smaller, so that inverted it will just
slip easily into the tank B. In the bottom, or rather the top
now, of tank A is cut a hole, and a little can, D, is fitted in
it and soldered. On top and over can D is soldered a large tin
can screw. A rubber washer is fitted on this so that when the
screw top, E, is turned on it, the joint will be gas tight.
Another can, C, which will just slip inside the little can, is
perforated with a number of holes. This can C is filled about
half full of broken pieces of carbide and then placed in the
little can D. A gas cock, H, is soldered onto tank A, as shown,
from which the gas may be taken through a rubber tube. Fill tank
B with water and set tank A into it. This will cause some air to
be enclosed, which can be released by leaving the cock open until
tank A settles down to the point where the water will begin to
run in the perforations of the little tank. The water then comes
in contact with the carbide and forms gas, which expands and
stops the lowering of tank A. Then the cock must be closed and
tubing attached. It is dangerous to attempt to strike a match to
light a jet or the end of the cock while air is escaping and
just as the first gas is being made. Wait until the tank is well
raised up before doing this.

Contributed by James E. Noble, Toronto, Ont.

Homemade Annunciator

Annuciator and Wiring Diagram

When one electric bell is operated from two push-buttons it is
impossible to tell which of the two push-buttons is being
operated unless an annunciator or similar device is used. A very
simple annunciator for indicating two numbers can be made from a
small box, Fig. 1, with an electric-bell magnet, A, fastened in
the bottom. The armature, B, is pivoted in the center by means of
a small piece of wire and has an indicator or hand, C, which
moves to either right or left, depending on which half of the
magnet is magnetized. If the back armature, D, of the magnet is
removed the moving armature will work better, as this will
prevent the magnetism from acting on both ends of the armature.

The wiring diagram, Fig. 2, shows how the connections are to be
made. If the pushbutton A is closed; the bell will ring and the
pointer will point at 1, while the closing of the push-button B
will ring the bell, and move the pointer to 2.

Contributed by H. S. Bott, Beverly, N. J.

How to Make a Box Kite

Detail of Box Kite

As some of the readers of Amateur Mechanics may desire to build a
box kite, a simple method of constructing one of the modern type
is given in detail as follows: The sticks should be made of
straight grained wood, which may be either spruce, basswood or
white pine. The longitudinal corner spines, A A, should be 3/8
in. square by 42 in. long, and the four diagonal struts, B,
should be 1/4 in. by 1/2 in., and about 26 in. long. Two cloth
bands should be made to the exact dimensions given in the sketch
and fastened to the four longitudinal sticks with 1 oz. tacks. It
is well to mark the positions of the sticks on the cloth bands,
either with a soft lead-pencil or crayon, in order to have the
four sides of each band exactly equal. The ends of the bands
should be lapped over at least 1/2 in. and sewed double to give
extra strength, and the edges should be carefully hemmed, making
the width, when finished, exactly 12 in. Probably the best cloth
for this purpose is nainsook, although lonsdale cambric or
lightweight percaline will answer nearly as well.

The diagonal struts, B, should be cut a little too long, so that
they will be slightly bowed when put in position, thus holding
the cloth out taut and flat. They should be tied together at the
points of intersection and the ends should be wound with coarse
harness maker’s thread, as shown at C, to prevent splitting. The
small guards, D, are nailed or glued to the longitudinal sticks
to prevent the struts slipping out of position. Of course the
ends of the struts could be fastened to the longitudinal strips
if desired, but if made as described the kite may be readily
taken apart and rolled up for convenience in carrying.

The bridle knots, E, are shown in detail at H and J. H is a
square knot, which may be easily loosened and shifted to a
different position on the bridle, thus adjusting the lengths of F
and G. A bowline knot should be tied at J, as shown, to prevent
slipping. If the kite is used in a light wind, loosen the square
knot and shift nearer to G, thus shortening G and lengthening F,
and if a strong wind is blowing, shift toward F, thereby
lengthening G and making F shorter. In a very strong wind do not
use the bridle, but fasten a string securely to the stick at K.

Contributed by Edw. E. Harbert, Chicago.

Lubricating a Camera Shutter

An experienced photographer uses blacklead [graphite] for grooves
about a camera or holder. A small quantity is rubbed well into
the grooves and on the edges of shutters, that refuse to slide
easily, with gratifying results. Care must be taken to allow no
dust to settle in the holders, however.

Simple Open-Circuit Telegraph Line

Simple Telegraph Line

By using the circuit shown in the sketch for short-distance
telegraph lines, the extra switches and wiring found in many
circuits are done away with. Closing either key will operate both
sounders, and, as the resistance of the sounders is very high,
the batteries do not run down for a long time.

Contributed by A. D. Stoddard, Clay Center, Kan.

How to Make a Thermo Battery

Thermo Battery

A thermo battery, for producing electricity direct from heat, can
be made of a wooden frame, A, with a number of nails, B, driven
in the vertical piece and connected in series with heavy copper
wires, C. The connections should all be soldered to give good
results, as the voltage is very low and the resistance of an
unsoldered joint would stop the current.

The heat may be supplied by an alcohol lamp or other device, and
the current may then be detected by means, of a simple
galvanometer consisting of a square spool of No. 14 or No. 16
single-covered wire, E, with a pocket compass, F, placed on top.
Turn the spool in a north and south direction, or parallel with
the compass needle. Then, when the nail heads are heated and the
circuit completed, the needle will swing around it at right
angles to the coils of wire. Applying ice or cold water to the
nail heads will reverse the current.

Contributed by A. C. A., Chicago.

How to Discharge a Toy Cannon by Electricity

Electrical Attachment for Discharging Toy Cannon

A device for discharging a toy cannon by electricity can be
easily made by using three or four dry batteries, a switch and a
small induction coil capable of giving a 1/8-in. spark. Fasten a
piece of wood, A, to the cannon, by means of machine screws or,
if there are no trunnions on the cannon, the wood may be made in
the shape of a ring and slipped on over the muzzle. The fuse hole
of the cannon is counterbored as shown and a small hole is
drilled at one side to receive a small piece of copper wire, E.
The wood screw, C, nearly touches E and is connected to one
binding post of the induction coil. The other binding post is
connected with the wood screw, D, which conducts the current into
the cannon, and also holds the pieces of wood, A and B, in
position.

When the cannon is loaded, a small quantity of powder is placed
in the counterbore, and the spark between C and E ignites this
and discharges the cannon. A cannon may be fired from a distance
in this way, and as there is no danger of any spark remaining
after the current is shut off, it is safer than the ordinary
cannon which is fired by means of a fuse.

Contributed by Henry Peck, Big Rapids, Mich.

Simple Electric Lock

Lock Operated by a Magnet

The illustration shows an automatic lock operated by electricity,
requiring a strong magnet, but no weights or strings, which
greatly simplifies the device over many others of the kind.

The weight of the long arm, L, is just a trifle greater than the
combined weights of the short arms, A and S. The fulcrum of the
lever is at C, where there is a staple. The lever swings on one
arm of the staple and the other arm is so placed that when the
lever is in an upright position, with the long arm at L’, it will
not fall because of its greater weight but stays in the position
shown. The purpose of this is to leave the short arm, A, when in
position at A’, within the reach of the magnet. Arm L rests on an
L-shaped hook, H; in this position the door is locked.

To unlock the door, press the button, B. The momentum acquired
from the magnet by the short arms, A and S, is sufficient to move
the long arm up to the position of L’. To lock the door, press
the button and the momentum acquired from the magnet by the short
arms, now at A’ and S’, is sufficient to move the long arm down
from L’ to the position at L.

Contributed by Benjamin Kubelsky, Chicago.

Direct-Connected Reverse for Small Motors

Direct-Connected Reverse

A simple reverse for small motors can be attached directly to the
motor as shown in Fig. 1. Fig. 2 shows the construction of the
reverse block: A is a strip of walnut 5/8 in. square and 3/8 in.
thick with strips of brass or copper (BB) attached as shown.
Holes (CC) are drilled for the wire connections and they must be
flush with the surface of the block. A hole for a 1/2 in. screw
is bored in the block. In Fig. 1, D is a thin strip of walnut or
other dense, hard wood fitted to the binding posts of the brush
holders, to receive the screw in the center.

Before putting the reverse block on the motor, remove all the
connections between the lower binding posts and the brush holders
and connect both ends of the field coil to the lower posts. Bend
the strips BB (Fig. 2) to the proper position to make a wiping
contact with the nuts holding the strip of wood D, Fig. 1. Put
the screw in tight enough to make the block turn a little hard.
Connect as shown in the illustration. To reverse, turn the block
so the strips change connections and the motor will do the rest.

Contributed by Joseph B. Keil, Marion, Ohio.

A Handy Ice Chisel

Combination Ax and Ice Chisel

Fishing through the ice is great sport, but cutting the first
holes preparatory to setting the lines is not always an easy
task. The ice chisel here described will be found very handy, and
may be made at very slight expense.

In the top of an old ax-head drill a 9/16-in. hole, and then tap
it for a 3/8-in. gas-pipe, about 18 in. long. Thread the other
end of the pipe, and screw on an old snow-shovel handle. When
ready for use, screw the two pieces together and you have your
chisel complete.

A short ax-handle may be included in the outfit. When the holes
are finished and your lines set, unscrew the pipe from the head
of the ax, put in the handle, and your ax is ready to cut the
wood to keep your fire going.

Contributed by C. J. Rand, West Somerville, Mass.

More Uses for Pipe Fittings

Lamp Shade and Dumbbell

It would seem that the number of useful articles that can be made
from pipes and fittings is unlimited. The sketch shows two more
that may be added to the list. A and B are front and side views
of a lamp-screen, and C is a dumbbell. The lamp shade is
particularly useful for shading the eyes when reading or writing
and, if enameled white on the concave side, makes an excellent
reflector for drawing at night, or for microscopic work.

The standard and base, consisting of an ordinary pipe flange
bushed down to receive the upright nipple, are enameled a jet
black, and if the device is to be used on a polished table, a
piece of felt should be glued to the bottom. A good way to hold
the fan in the nipple is to use a small wedge.

The dumbbells are made of short pieces of 3/4-in. pipe with
1-2-in. couplings fastened to each end by pouring
melted lead in
the space between the pipes and the couplings. The appearance is
greatly improved by enameling black, and if desired the handles
may be covered with leather.

Contributed by C. E. Warren, M. D., North Easton, Mass.

Sealing-Wax Bent While Cold

Bending Cold Sealing-Wax

If a piece of sealing-wax is supported in a horizontal position
by one end, as shown at A in the sketch, it will gradually bend
to the shape indicated by the dotted lines B. To attempt bending
it with the hands would result in breaking it unless a steady
pressure were applied for a long time. This peculiar property is
also found in ice.

Homemade Pottery Kiln

Homemade Pottery Kiln

A small kiln for baking clay figures may be built at a cost of
$1. The following shows the general plan of such a kiln which has
stood the test of 200 firings, and which is good for any work
requiring less than 1400° C.

Get an iron pail about 1 ft. high by 1 ft. across, with a cover.
Any old pail which is thick enough will do, while a new one will
cost about 80 cents. In the bottom of this cut a 2-in. round hole
and close it with a cork or wood plug, A, Fig. 1, which shall
project at least 2 in. inside the pail. Make a cylindrical core
of wood, B, Fig. 1, 8 in. long and 8 in. across. Make a mixture
of clay, 60%; sand, 15%; and graphite, 25%, kneading thoroughly
in water to a good molding consistency. Line the pail, bottom and
sides, with heavy paper and cover the core with same. Now pack
the bottom of the pail thoroughly with a 2-in. layer of the clay
mixture, and on it set the paper wrapped core, carefully
centering it. The 2 in. of space between the core and the sides
of the pail all around is to be filled with clay, C, as is shown
in the sketch, using a little at a time and packing it very
tight. In like manner make the cover of the kiln, cutting the
hole a little smaller, about 1 in. At the edge or rim of the
cover encircle a 2-in. strip of sheet iron, E, Fig. 2, to hold
the clay mixture, C. Set aside for a few days until well dried.

While these are drying you may be making a muffle, if there is to
be any glazing done. This is a clay cylinder (Fig. 3) with false
top and bottom, in which the pottery to be glazed is protected
from any smoke or dust. It is placed inside the kiln, setting on
any convenient blocks which will place it midway. The walls of
the muffle should be about 1/2 in. thick, and the dimensions
should allow at least 1 in. of space all around for the passage
of heat between it and the walls of the kiln. By the time the
clay of the kiln is well dried, it will be found that it has all
shrunk away from the iron about 3/8 in. After removing all the
paper, pack this space-top, bottom and sides-with moist ground
asbestos.
If the cover of the pail has no rim, it may be fastened
to the asbestos
and clay lining by punching a few holes, passing
wire nails through and clinching them. Fit all the parts together
snugly, take out the plugs in the top and bottom, and your kiln
is ready for business. The handle of the pail will be convenient
for moving it about, and it can be set on three bricks or some
more elaborate support, as dictated by fancy and expense.

The temperature required for baking earthenware is 1250°-1310°,
C.; hotel china, 1330°; hard porcelain, 1390°-1410°. These
temperatures can not be obtained in the above kiln by means of
the ordinary Bunsen burner. If will be necessary either to buy
the largest size Bunsen, or make one yourself, if you have the
materials. If you can get a cone which can be screwed into an
inch pipe, file the opening of the cone to 1/16 in. diameter, and
jacket the whole with a 2-1/2-in. pipe. The flame end of this
burner tube should be about 4-1/2 in. above the cone opening and
should be covered with gauze to prevent flame from snapping back.
When lighted, the point of the blue flame, which is the hottest
part, should be just in the hole in the bottom of the kiln. Such
a burner will be cheaply made and will furnish a kiln temperature
of 1400 degrees, but it will burn a great deal of gas.

A plumber’s torch of medium size will cost more in the beginning,
but will be cheaper in operation. Whatever burner is used, the
firing should be gradual, and with especial caution the first
time. By experiment you will find that a higher temperature is
obtained by placing a 1-in. pipe 2-ft. long over the lid hole as
a chimney. It would be still more effective to get another iron
pail, 2 in. wider than the kiln, and get a down draft by
inverting it over the kiln at whatever height proves most
suitable.

G. L. W.

How to Make a Small Medical Induction Coil

Medical Induction Coil

The coil to be described is 3-1/2 in., full length of iron core,
and 3/4 in. in diameter.

Procure a bundle of small iron wire, say 1/4 in. in diameter, and
cut it 3-1/2 in. long; bind neatly with coarse thread and file
the ends smooth (Fig. 1). This done, make two wood ends, 1-1/4 by
1-1/4 in. and 3/8 in. thick, and varnish. Bore holes in the
center of each so the core will fit in snugly and leave about 1/4
in. projecting from each end (Fig. 1).

After finishing the core, shellac two layers of thick paper over
it between the ends; let this dry thoroughly. Wind two layers of
bell magnet wire over this, allowing several inches of free wire
to come through a hole in the end. Cover with paper and shellac
as before.

Wind about 1/8 in. of fine wire, such as used on telephone
generators, around the coil, leaving long terminals. Soak the
whole in melted paraffin and let cool; bind tightly with black
silk.

The vibrator is made of a piece of thin tin to which is soldered
the head of an iron screw and on the other side a small piece of
platinum, which can be taken from an old electric bell (Fig. 2).

Of course, a regulator must be had for the vibrator; this can be
accomplished by bending a stout piece of copper wire as shown.
The connections and the base for setting up are shown in the
figures.

Contributed by J. T. R., Washington, D. C.

Mechanical Trick With Cards

Card Trick

The following mechanical card trick is easy to prepare and simple
to perform:

First, procure a new deck, and divide it into two piles, one
containing the red cards and the other the black ones, all cards
facing the same way. Take the red cards, square them up and place
in a vise. Then, with a plane, plane off the upper right hand
corner and lower left hand corner, as in Fig. 1, about 1/16 in.

Then take the black cards, square them up, and plane off about
1/16 in. on the upper left hand corner and lower right hand
corner, as in Fig. 2.

Next restore all the cards to one pack, taking care to have the
first card red, the next black, and so on, every alternate card
being the same color. Bend the pack so as to give some spring to
the cards, and by holding one thumb on the upper left-hand corner
all the cards will appear red to the audience; place thumb in the
center at top of pack and they will appear mixed, red and black;
with thumb on upper right-hand corner all cards appear black. You
can display either color called for.

Contributed by Ralph Gingrich, Chicago.

How to Make a Rain Gauge

Rain Gauge

An accurate rain gauge may be easily constructed from galvanized
iron, as shown in the sketch herewith. The funnel, A, overlaps
and rests on the body, B, and discharges into the tube, C, the
area of which is one-tenth that of the top of the funnel. The
depth of the water in C is thus ten times the actual rainfall, so
that by measuring it with a stick marked off in tenths of an
inch, we obtain the result in hundredths of an inch.

A good size to make the rain gauge is as follows: A, 8 in.
diameter; C, 2.53 in.; length of C, about 20 in. It should be
placed in an exposed location, so that no inaccuracy will occur
from wind currents. To find the fall of snow, pour a known
quantity of warm water on the snow contained in the funnel and
deduct the quantity poured in from the total amount in the tube.

Contributed by Thurston Hendrickson, Long Branch, N.J.

How to Make an Aquarium

Detail of Aquarium Frame

Aquarium Finished

In making an aquarium, the first thing to decide on is the size.
It is well not to attempt building a very large one, as the
difficulties increase with the size. A good size is 12 by 12 by
20 in., and this is inexpensive to build. First buy one length of
3/4 by 1/8-in. angle iron for the frame, F, Fig. 1. This can be
obtained at any steel shop and should cost about 20 cents. All
the horizontal pieces, B, should be beveled 45° at the ends and
drilled for 3/16 in. stove bolts. The beveling may be done by
roughing out with a hacksaw and finishing with a file. After all
the pieces are cut and beveled they should be drilled at the ends
for the 3/16-in. stove bolts, C. Drill all the horizontal pieces,
B, first and then mark the holes on the upright pieces, A,
through the holes already drilled, thus making all the holes
coincide. Mark the ends of each piece with a figure or letter, so
that when they are assembled, the same ends will come together
again. The upright pieces, A, should be countersunk as shown in
the detail, and then the frame is ready to assemble.

After the frame has been assembled take it to glazier and have a
bottom made of skylight glass, and sides and ends of double-thick
window glass. The bottom glass should be a good fit, but the
sides and ends should be made slightly shorter to allow the
cement, E, to form a dovetail joint as shown. When the glass is
put in the frame a space, D, will be found between the glass and
the horizontal pieces, B, of the frame. If this were allowed to
remain the pressure of the water would spring the glass and cause
a leak at E; so it is filled up with plaster of paris.

The cement, E, is made as follows: Take 1 gill of plaster of
paris, 1 gill of litharge (lead monoxide),
1 gill of fine white sand, and 1/3 of
a gill of finely powdered rosin. Mix well and add boiled linseed
oil and turpentine until as thick as putty. Let the cement dry
three or four days before putting any water in the aquarium.

In choosing stock for the aquarium it should be remembered that a
sufficient quantity of vegetable life is required to furnish
oxygen for the fish. In a well balanced aquarium the water
requires renewal only two or three times a year. It is well to
have an excess of plants and a number of snails, as the snails
will devour all the decaying vegetable matter which would
otherwise poison the water and kill the fish.

If desired, a centerpiece (A, Fig. 2) can be made of colored
stones held together by cement, and an inverted jar can be
supported in the position shown at B. If the mouth of the jar is
below the surface of the water it will stay filled and allow the
fish to swim up inside as shown. Some washed pebbles or gravel
should be placed on the bottom, and, if desired, a few Chinese
lilies or other plants may be placed on the centerpiece.

Homemade Pneumatic Lock

Pneumatic Door-Opener

Mount an old bicycle hand-pump, A, on the door by means of a
metal plate, B, having a swinging connection at C. Fasten the
lever, D, to the door knob, and make a hinge connection with the
pump by means of a piece of sheet brass, E, soldered to the end
of the cylinder. All this apparatus is on the inside of the door
and is connected by a small rubber tube, F, to a secret
mouthpiece placed at some convenient location. A small piece of
spring brass, screwed to the door frame, will open the door about
1/2 in. when the operator blows in the mouthpiece, or if the door
is within reach of the mouthpiece, the operator may push the door
at the same time that he blows, thus doing away with the spring,
which is only used to keep the door from relocking.

One way of making the air connection with the outside is to bend
the tube F around and stick it through the keyhole. Few burglars
would ever think to blow in the keyhole.

Contributed by Orton E. White, Buffalo, N. Y.

A Homemade Water Motor
By Mrs. Paul S. Winter

Detail of Homemade Waterwheel

In these days of modern improvements, most houses are equipped
with a washing machine, and the question that arises in the mind
of the householder is how to furnish the power to run it
economically. I referred this question to my husband, with the
result that he built a motor which proved so very satisfactory
that I prevailed upon him to give the readers of Amateur
Mechanics a description of it, hoping it may solve the same
question for them.

A motor of this type will develop about 1/2 hp. with a water
pressure of 70 lb. The power developed is correspondingly
increased or decreased as the pressure exceeds or falls below
this. In the latter case the power may be increased by using a
smaller pulley. Fig. 1 is the motor with one side removed,
showing the paddle-wheel in position; Fig. 2 is an end view; Fig.
3 shows one of the paddles, and Fig. 4 shows the method of
shaping the paddles. To make the frame, several lengths of
scantling 3 in. wide by 1 in. thick (preferably of hard wood) are
required. Cut two of them 4 ft. long, to form the main supports
of the frame, AA, Fig. 1; another, 2 ft. 6 in. long, for the
top, B, Fig. 1; another, 26 in. long, to form the slanting part,
C, Fig. 1; and another, D, approximately 1 ft., according to the
slant given C. After nailing these together as shown in the
illustration, nail two short strips on each side of the outlet,
as at E, to keep the frame from spreading.

Cut two pieces 30 in. long. Lay these on the sides of the frame
with their center lines along the line FF, which is 15 in. from
the outside top of the frame. They are shown in Fig. 2 at GG. Do
not fasten these boards now, but mark their position on the
frame. Two short boards 1 in. wide by 1 in. thick (HH, Fig. 2)
and another 1 in. by 1-1/2 in. (I, Fig. 2) form a substantial
base.

Cut the wheel from sheet iron 1/16 in. thick, 24 in. in diameter.
This can be done roughly with hammer and chisel and then smoothed
up on an emery wheel, after which cut 24 radial slots 3/4 in.
deep on its circumference by means of a hacksaw. On each side of
the wheel at the center fasten a rectangular piece of 1/4-in.
iron 3 by 4 in. and secure it to the wheel by means of four
rivets; after which drill a 5/8 in. hole through the exact center
of the wheel.

Cut 24 pieces of 1/32-in. iron, 1-1/2 by 2-1/2 in. These are the
paddles. Shape them by placing one end over a section of 1-in.
pipe, and hammer bowl shaped with the peen of a hammer, as shown
in Fig. 4. Then cut them into the shape shown in Fig. 3 and bend
the tapered end in along the lines JJ, after which place them in
the slots of the wheel and bend the sides over to clamp the
wheel. Drill 1/8-in. holes through the wheel and sides of the
paddles and rivet paddles in place. Next secure a 5/8-in. steel
shaft 12 in. long to the wheel about 8 in. from one end by means
of a key. This is done by cutting a groove in the shaft and a
corresponding groove in the wheel and fitting in a piece of metal
in order to secure the wheel from turning independently of the
shaft. Procure two collars or round pieces of brass (KK, Fig. 2)
with a 5/8-in. hole through them, and fasten these to the shaft
by means of set screws to prevent it from moving lengthwise.

Make the nozzle by taking a piece of 1/2-in. galvanized pipe
3-1/2 in. long and filling it with babbitt metal; then drill a
3/16-in. hole through its center. Make this hole conical,
tapering from 3/16 in. to a full 1/2 in. This is best done by
using a square taper reamer. Then place the nozzle in the
position shown in Fig. 1, which allows the stream of water to
strike the buckets full in the center when they reach the
position farthest to the right.

Take the side pieces, GG, and drill a 1-in. hole through their
sides centrally, and a 1/4-in. hole from the tops to the 1-in.
holes. Fasten them in their proper position, with the wheel and
shaft in place, the shaft projecting through the holes just
mentioned. Now block the wheel; that is, fasten it by means of
wedges or blocks of wood until the shaft is exactly in the center
of the inch holes in the side pieces. Cut four disks of cardboard
to slip over the shaft and large enough to cover the inch holes.
Two of these are to be inside and two outside of the frames (one
to bear against each side of each crosspiece). Fasten these to
the crosspieces by means of tacks to hold them securely. Pour
melted babbitt metal into the 1/4-in. hole to form the bearings.
When it has cooled, remove the cardboard, take down the
crosspieces, and drill a 1/8-in. hole from the top of the
crosspieces through the babbitt for an oil-hole.

Secure sufficient sheet zinc to cover the sides of the frame. Cut
the zinc to the same shape as the frame and let it extend down to
the crosspieces EE. Tack one side on. (It is well to tack strips
of heavy cloth—burlap will do—along the edges under the
zinc to form a water-tight joint.) Fasten the crosspiece over the
zinc in its proper position. Drill a hole through the zinc, using
the hole in the crosspiece as a guide. Then put the wheel in a
central position in the frame, tack the other side piece of zinc
in place and put the other crosspiece in place. Place the two
collars mentioned before on the shaft, and fasten so as to bear
against the crosspieces, in order to prevent the wheel and shaft
from moving sidewise. If the bearings are now oiled, the shaft
should turn easily and smoothly. Fasten a pulley 4 or 6 in. in
diameter to the longest arm of the shaft. Connect the nozzle to a
water faucet by means of a piece of hose; place the outlet over a
drain, and belt the motor direct to the washing-machine, sewing
machine, ice-cream freezer, drill press, dynamo or any other
machinery requiring not more than 1/2 hp.

This motor has been in use in our house for two years in all of
the above ways, and has never once failed to give perfect
satisfaction. It is obvious that, had the wheel and paddles been
made of brass, it would be more durable, but as it would have
cost several times as much, it is a question whether it would be
more economical in the end. If sheet-iron is used, a coat of
heavy paint would prevent rust and therefore prolong the life of
the motor. The motor will soon pay for itself in the saving of
laundry bills. We used to spend $1 a month to have just my
husband’s overalls done at the laundry, but now I put them in the
machine, start the motor, and leave them for an hour or so. At
the end of this time they are perfectly clean, and I have noticed
that they wear twice as long as when I sent them to the laundry.

How to Make Silhouettes

Making a Silhouette with the Camera

Photography in all branches is truly a most absorbing occupation.
Each of us who has a camera is constantly experimenting, and
everyone of us is delighted when something new is suggested for
such experiments.

To use a camera in making silhouettes select a window facing
north if possible, or if used only at times when the sun is not
on it, any window will do, says the Photographic Times. Raise the
window shade half way, remove any white curtains there may be,
and in the center of the lower pane of glass paste by the four
corners a sheet of tissue paper that is perfectly smooth and
quite thick, as shown in the sketch at B. Darken the rest of the
window, shutting out all light from above and the sides. Place a
chair so that after being seated the head of the subject will
come before the center of the tissue paper, and as near to it as
possible, and when looking straight before him his face will be
in clear profile to the camera.

Draw the shades of all other windows in the room. Focus the
camera carefully, getting a sharp outline of the profile on the
screen. Do not stop down the lens, as this makes long exposure
necessary, and the subject may move.

Correct exposure depends, of course, on the lens, light and the
plate. But remember that a black and white negative is wanted
with as little detail in the features as possible. The best plate
to use is a very slow one, or what is called a process plate.

In developing get all possible density in the high lights,
without detail in the face, and without fog. Printing is best
done on contrasty development paper with developer not too
strong.

The ideal silhouette print is a perfectly black profile on a
white ground. With a piece of black paper, any shape in stopping
off print may be made as shown at C in the sketch.

How to Make a Galvanoscope

Galvanoscope

Interior View

A galvanoscope for detecting small currents of electricity can be
made from a coil of wire, A; a glass tube, B, full of water; a
core, C; and a base, D, with binding posts as shown. The core C,
which is made of iron and cork, is a trifle lighter than the
water it displaces and will therefore normally remain in the top
of the tube; but as soon as a current of electricity passes
through the coil, the core is drawn down out of sight. The
current required is very small, as the core is so nearly balanced
that the least attraction will cause it to sink.

The glass tube may be a test tube, as shown in Fig. 2, or an
empty developer tube. If one has neither a test tube nor
developer tube, an empty pill bottle may be used. The washers at
the ends of the coil can be made of fiber, hard rubber, or wood;
or can be taken from an old magnet. The base may be made of wood
or any other insulating material and should have four short legs
on the bottom. Make the coil of single-covered wire about No. 18
and connect ends to binding posts as shown in Fig. 2.

The core is made by pushing a small nail through a piece of cork.
It should be made so that it will rise slowly when placed under
water. Some filing may be necessary to get the weight just right,
but it should be remembered that the buoyancy of the core can be
adjusted after the parts are assembled, by pressing the cork in
the bottom of the test tube. This causes compression in the water
so that some is forced into the upper cork, reducing its
displacement and causing it to sink. The lower cork is then
slowly withdrawn, by twisting, until the core slowly rises.

The instrument will then be adjusted ready for use.

Connect the binding posts to a single cell of battery—any kind
will do, as a slight current will answer. On completing the
circuit the core will descend; or put in a switch or push button
on one of the battery wires. If the button be concealed where the
operator can reach it, the core will obey his command to rise or
fall, according to his control of the current. This is a
mysterious looking instrument, the core being moved without
visible connection to any other part.

Lubricating Sheet Metal

To lubricate sheet metal mix 1 qt. whale oil, 1 lb.
white lead, 1 pt. water and 3 oz. finest
graphite. Apply with a brush before the metal enters the dies.

An Optical Top

An Optical Top

One of the latest optical delusions, and one not easy to explain,
is Benham’s color top. Cut out the black and white disk shown in
the figure, and paste on a piece of stiff cardboard. Trim the
edges of the cardboard to match the shape of the disk, and make a
pinhole in the center. Cut the pin in half and push it through
from the under side until the head of the pin touches the
cardboard. Spin slowly in a strong light and some of the lines
will appear colored. The colors appear different to different
people, and are changed by reversing the rotation.

Card Trick with a Tapered Deck

Cards from a Tapered Deck

Another simple trick to perform but one not easily detected, is
executed by using a tapered deck of cards as shown in Fig. 1. A
cheap deck of cards is evened up square, fastened in a vise and
planed along the edge in such a manner that all the pack will be
tapered about 1/16 in. This taper is exaggerated in the
illustration which shows one card that has been turned end for
end.

It is evident that any card reversed in this way can be easily
separated from the other cards in the pack, which makes it
possible to perform the following trick: The performer spreads
the cards out, fan-like, and asks an observer to withdraw a card,
which is then replaced in any part of the pack. After thoroughly
shuffling the cards the performer then holds the deck in both
hands behind his back and pronouncing a few magic words, produces
the card selected in one hand and the rest of the pack in the
other. This is accomplished by simply turning the deck end for
end while the observer is looking at his card, thus bringing the
wide end of the selected card at the narrow end of the pack when
it is replaced. The hands are placed behind the pack for a double
purpose, as the feat then seems more marvelous and the observers
are not allowed to see how it is done.

In prize games, players having the same score are frequently
called upon to cut for low to determine which shall be the
winner, but a fairer way is to cut for high as a person familiar
with the trick shown in Fig. 2 can cut the cards at the ace,
deuce, or three spot, nearly every time, especially if the deck
is a new one. This is done by simply pressing on the top of the
deck as shown, before cutting, thus causing the increased ink
surface of the high cards to adhere to the adjacent ones. A
little practice will soon enable one to cut low nearly every
time, but the cards must be grasped lightly and the experiment
should be performed with a new deck to obtain successful results.

Contributed by D.B.L., Chicago.

A Constant-Pressure Hydrogen Generator

By fitting three bottles, A, B, C, with rubber stoppers and
connecting with glass tubes as shown in the sketch,
hydrogen or
other gases produced in a similar manner may be generated under
constant pressure. In making hydrogen,
bottle B is partly filled
with zinc nodules formed by slowly pouring melted zinc into
water. Hydrochloric acid is then poured in the small funnel, thus
partly filling bottles A and C. When the acid rising from C comes
in contact with the zinc, hydrogen
gas is generated and fills
bottle B. The gas continues to generate until the pressure is
sufficient to force the acid back down the tube into bottle C,
when the action ceases. As fast as the gas is used the acid rises
in the tube and generates more, thus keeping the pressure nearly
constant, the pressure depending on the difference between the
levels of the acid in bottle A and bottle B. As this device is
easily upset, a ring-stand should be used to prevent its being
broken, or if it is to be a permanent apparatus it may be mounted
on a substantial wooden base. This apparatus may also be used for
preparing acetylene
gas or almost any gas which requires a
mixture of a solid and liquid in its preparation.

Contributed by C. S. J., Detroit.

[Transcriber’s note: I recall doing this experiment in a college
chemistry lab. The instructor warned us to drape the experiment
with a cloth before adding the acid. Ten minutes later there
began a series of small explosions throughout the lab.]

Restoring Tone to a Cracked Bell

Many a bell with a deadened tone due to a cracked rim, can be
given its original clear ringing sound by sawing out the crack
with a common hacksaw. Make the saw cut along the line of the
crack. The opening caused by the saw will allow the free
vibration of the metal.

Contributed by F. W. Bently, Jr., Huron, S. Dak.

How to Make a Paper Phonograph Horn

Detail of Phonograph Horn

Secure a piece of tubing about 1-3/4 in. long that will fit the
connection to the reproducer, and wrap a quantity of heavy thread
around one end as shown in the enlarged sketch A, Fig. 1. Form a
cone of heavy paper, 9 in. long and 3 in. in diameter, at the
larger end with the smaller end to fit the diameter of the tube
A, making it three-ply thick and gluing the layers together.
Attach this cone on the tube A where the thread has been wrapped
with glue, as shown in Fig. 2. Fig. 2 is also an enlarged sketch.
Make ten pieces about 1 ft. 10 in. in length and 3 in. wide from
the thin boards of a biscuit or cracker box. Cut an arc of a
circle in them on a radius of 2 ft. (Fig. 3). Make a 10-sided
stick, 12 in. long, that will fit loosely in the tube A, to which
nail the 10 pieces as shown in Fig. 4, connecting the bottom by
cross pieces, using care to keep them at equal distances apart
and in a circle whose diameter is about 2 ft.

The cone is placed over the stick as shown by the dotted lines in
Fig. 4 and temporarily fastened in position. Cut out paper
sections (Fig. 5) that will cover each space between the 10
pieces, allowing 1 in. on one side and the top, in which to cut
slits that will form pieces to overlap the next section and to
attach with glue. Fasten the sections all around in like manner.
The next course is put on in strips overlapping as shown at B,
Fig. 6. Finish by putting on sections in the same way as the
first course, making it three-ply thick. Remove the form, trim to
suit and glue a piece of paper over the edge. When the glue is
thoroughly hardened, put on two coats of white and one of blue
paint, shading it to suit and striping it with gold bronze.

How to Make a Hygrometer

The Hygrometer

A homemade hygrometer, for determining the degree of moisture in
the atmosphere, is shown in the accompanying sketch and consists
of a board, A, with a nail at each end to hold the silk thread B.
A second piece of silk thread, C, is tied to the center of B and
connects with an indicating hand or pointer supported by the
bracket D. The axle on which the pointer revolves consists of a
piece of round wood, about the size of a lead-pencil, with a pin
driven in each end. A piece of tin, E, is cut V-shaped at each
end and bent up at the ends to form bearings for the pins. The
silk thread C is fastened to the wooden axle and is wrapped one
or two turns around it, so that when the thread is pulled the
pointer will move on the scale. It will be noticed that the
thread B is not perfectly straight, but bends toward D. For this
reason a very small shrinkage of B, such as occurs when the
atmosphere is dry, will cause an increased movement of C, which
will be further increased in the movement of the pointer. An
instrument of this kind is very interesting and costs nothing to
make.

Contributed by Reader, Denver.

The Protection of a Spring Lock

After shutting the front door and hearing the spring lock snap
into its socket, most people go off with a childlike faith in the
safety of their goods and chattels. But the cold fact is that
there is scarcely any locking device which affords less
protection than the ordinary spring lock. It is the simplest
thing in the world for a sneak thief to slip a thin knife between
the door-casing and the strip, push back the bolt, and walk in.

Fortunately, it is equally easy to block that trick. Take a
narrow piece of tin 3 or 4 in. long, bend it at right angles
throughout its length, and tack it firmly in the angle between
the casing and strip, so as to make it impossible to reach the
bolt without tearing off the strip.

Another way is to drive nails through the strip at intervals of
half an inch, enough to protect the bolt from being meddled with.

A Controller and Reverse for a Battery Motor

Motor Reverse and Controller

Secure a cigar or starch box and use to make the base, B. Two
wood-base switches, S S, are cut off a little past the center and
fastened to the base with a piece of wood between them. The upper
switch, S, is connected to different equal points on a coil of
wire, W, while the lower switch, S, is connected each point to a
battery, as shown. The reverse switch, R, is made from two brass
or copper strips fastened at the top to the base with screws and
joined together by a piece of hard rubber or wood with a small
handle attached. Connect wires A to the armature and wires F to
the field of the motor. By this arrangement one, two or three and
so on up until all the battery cells are used and different
points of resistance secured on the coil of wire. The reverse
lever when moved from right to left, or left to right, changes
the direction of the armature in the motor from one way to the
other.

Contributed by J. Fremont Hilscher, Jr., West St. Paul, Minn.

How to Build a Grape Arbor

Grape-Arbor Trellis

A grape arbor made of white pine, put together as shown in the
sketch, will last for several years. The 2 by 4-in. posts, A, are
7 ft. long. The feet, B, are made 2 by 4 in., 4 ft. long, and
rest on a brick placed under each end.

How to Make a Toy Steam Engine

Toy Steam Engine Assembled

Valve Motion and Construction of Piston

Engine in Operation

A toy engine can be easily made from old implements which can be
found in nearly every house.

The cylinder A, Fig. 1, is an old bicycle pump, cut in half. The
steam chest D, is part of the piston tube of the same pump, the
other parts being used for the bearing B, and the crank bearing
C. The flywheel Q can be any small-sized iron wheel; either an
old sewing-machine wheel, pulley wheel, or anything available. We
used a wheel from an old high chair for our engine. If the bore
in the wheel is too large for the shaft, it may be bushed with a
piece of hard wood. The shaft is made of heavy steel wire, the
size of the hole in the bearing B.

The base is made of wood, and has two wood blocks, H and K, 3/8
in. thick, to support bearing B, and valve crank S, which is made
of tin. The hose E connects to the boiler, which will be
described later. The clips FF are soldered to the cylinder and
nailed to the base, and the bearing B is fastened by staples.

The valve motion is shown in Figs. 2 and 3. In Fig. 2 the steam
is entering the cylinder, and in Fig. 3 the valve B has closed
the steam inlet and opened the exhaust, thus allowing the steam
in the cylinder to escape.

The piston is made of a stove bolt, E, Fig. 2, with two washers,
FF, and a cylindrical piece of hard wood, G. This is wound with
soft string, as shown in Fig. 3, and saturated with thick oil. A
slot is cut in the end of the bolt E, to receive the connecting
rod H. The valve B is made of an old bicycle spoke, C, with the
nut cut in half and filed down as shown, the space between the
two halves being filled with string and oiled.

The valve crank S, Fig. 1, is cut out of tin, or galvanized iron,
and is moved by a small crank on the shaft. This crank should be
at right angles to the main crank.

The boiler, Fig. 4, can be an old oil can, powder can, or a syrup
can with a tube soldered to it, and is connected to the engine by
a piece of rubber tubing. The heat from a small gas stove will
furnish steam fast enough to run the engine at high speed.

This engine was built by W. G. Schuh and A. J. Eustice, of Cuba, Wis.

Writing with Electricity

Electrolytic Writing

Soak a piece of white paper in a solution of potassium iodide and
water for about a minute and then lay it on a piece of sheet
metal. Connect the sheet metal with the negative or zinc side of
a battery and then, using the positive wire as a pen, write your
name or other inscription on the wet paper. The result will be
brown lines on a white background.

Contributed by Geo. W. Fry, San Jose, Cal.

To Photograph a Man in a Bottle

Neither a huge bottle nor a dwarfed man is necessary for this
process, as it is merely a trick of photography, and a very
amusing trick, at that.

First, photograph the person to be enclosed in the bottle against
a dark plain background and mark the exact position on the ground
glass. Let the exposure be just long enough to show the figure
distinctly. Then place an empty bottle against a dark background
and focus so as to have the outlines of the bottle enclose those
of the man. Let this exposure be about twice the length of the
first, and the desired result is obtained.

A Musical Windmill

Make two wheels out of tin. They may be of any size, but wheel A
must be larger than wheel B. On wheel A fasten two pieces of
wood, C, to cross in the center, and place a bell on the four
ends, as shown. The smaller wheel, B, must be separated from the
other with a round piece of wood or an old spool. Tie four
buttons with split rings to the smaller wheel, B. The blades on
the wheels should be bent opposite on one wheel from the others
so as to make the wheels turn in different directions. When
turning, the buttons will strike the bells and make them ring
constantly.

Optical Illusions

Move These Figures Rapidly with a Rinsing Motion

By giving the page a revolving or rinsing motion the three
circular figures printed on the next page appear to rotate. The
best effect will be produced by laying the book down flat on the
desk or table and revolving, first in one direction and then in
the opposite direction, in such a way that any given point on the
page will describe a circle of about 1/2 in. diameter. Fig. 1
then appears to rotate in the same direction as the revolution;
Fig. 2 appears to revolve in the opposite direction, and Fig. 3
appears to revolve sometimes in the same direction and at other
times in the opposite direction.

A curious effect can be produced with Fig. 1 by covering up Figs.
2 and 3 with a piece of plain paper and laying a coin or other
small object on the paper. If the vision is then concentrated on
the coin or other object while same is being revolved, Fig. 1
will be seen to rotate.

Barrel-Stave Hammock

Cheap and Comfortable

A hammock made of barrel staves is more comfortable than one
would think, considering the nature of the material employed in
making it. Good smooth staves should be selected for this
purpose, and if one cares to go to little trouble a thorough
sandpapering will make a great improvement. Cut half circles out
of each stave, as shown at AA, and pass ropes around the ends as
shown at B. When finished the weight will then be supported by
four ropes at each end, which allows the use of small sized
ropes, such as clothes lines. A hammock of this kind may be left
out in the rain without injury.

Contributed by H.G.M., St. Louis, Mo.

A Singing Telephone

To Make a Telephone Sing

Those who have not already tried the experiment may be interested
to know that a telephone may be made to sing by holding the
receiver about 1/16 in. from the transmitter, as shown in the
illustration. The experiment will work well on most telephones,
but not on all.

When the receiver is placed in the position shown it acts like an
ordinary buzzer, and the function of the transmitter will then be
that of an interrupter. The slightest movement of the
transmitter diaphragm will cause an increased movement of the
receiver diaphragm. This in turn will act on the transmitter,
thus setting up sympathetic vibrations between the two, which
accounts for the sound.

A Microscope Without a Lens
By E. W. Davis

Detail of Lensless Microscope

Nearly everyone has heard of the pin-hole camera, but the fact
that the same principle can be used to make a microscope, having
a magnifying power of 8 diameters (64 times) will perhaps be new
to some readers.

To make this lensless microscope, procure a wooden spool, A (a
short spool, say 1/2 or 3/4 in. long, produces a higher
magnifying power), and enlarge the bore a little at one end. Then
blacken the inside with india ink and allow to dry. From a piece
of thin transparent celluloid or mica, cut out a small disk, B,
and fasten to the end having the enlarged bore, by means of
brads. On the other end glue a piece of thin black cardboard, C,
and at the center, D, make a small hole with the point of a fine
needle. It is very important that the hole D should be very
small, otherwise the image will be blurred.

To use this microscope, place a small object on the transparent
disk, which may be moistened to make the object adhere, and look
through the hole D. It is necessary to have a strong light to get
good results and, as in all microscopes of any power, the object
should be of a transparent nature.

The principle on which this instrument works is illustrated in
Fig. 2. The apparent diameter of an object is inversely
proportional to its distance from the eye, i. e., if the distance
is reduced to one-half, the diameter will appear twice as large;
if the distance is reduced to one-third, the diameter will appear
three times as large, and so on. As the nearest distance at which
the average person can see an object clearly is about 6 in., it
follows that the diameter of an object 3/4 in. from the eye would
appear 8 times the normal size. The object would then be
magnified 8 diameters, or 64 times. (The area would appear 64
times as large.) But an object 3/4-in. from the eye appears so
blurred that none of the details are discernible, and it is for
this reason that the pin-hole is employed.

Viewed through this microscope, a fly’s wing appears as large as
a person’s hand, held at arm’s length, and has the general
appearance shown in Fig. 3. The mother of vinegar examined in the
same way is seen to be swarming with a mass of wriggling little
worms, and may possibly cause the observer to abstain from all
salads forever after. An innocent-looking drop of water, in which
hay has been soaking for several days, reveals hundreds of little
infusoria, darting across the field in every direction. These and
hundreds of other interesting objects may be observed in this
little instrument, which costs little or nothing to make.

How to Make a Telegraph Key and Sounder

Sounder-A, brass: B, wood: C, soft iron; DD, coils wound with No.
26 wire: E, nail soldered on A; FF, binding posts: H spring

KEY-A, wood; B, brass or iron soldered to nail; C, brass; D,
brass: E, wood: F, connection of D to nail; HH, binding posts

The sounder, Fig. 1, is made from an old electric-bell magnet, D,
fastened to a wooden base. The lever, A, can be made of brass and
the armature, C, is made of iron. The pivot, E, is made from a
wire nail and is soldered to A. It should be filed to a point at
each end so as to move freely in the bearings, B, which are
pieces of hard wood.

The spring, H, is fastened at each end by pins, bent as shown,
and should not be too strong or the magnet will be unable to move
the armature. The stop, K, is a wire nail driven deep enough in
the base to leave about 1/8 in. between the armature and the
magnet. The binding posts, F, may be taken from old dry batteries
and are connected to the two wires from the magnet by wires run
in grooves cut in the base.

The base of the key, Fig. 2, is also made of wood and has two
wooden bearings, E, which are made to receive a pivot, similar to
the one used in the sounder. The lever of the key is made of
brass and has a hardwood knob, A, fastened near the end. A
switch, D, connects with the pivot at F and can be either made
from sheet brass, or taken from a small one-point switch. The
binding posts are like those of the sounder, and are connected to
the contacts, K, by wires run in grooves cut in the wood.

How to Make a Music Cabinet

How to Make a Music Cabinet

A neat music cabinet can be made as shown in the accompanying
sketch. Each side, AA, Fig. 1, is cut from a board about 36 in.
in length and 16 in. wide. Both are alike and can be cut from the
same pattern. As the front legs curve out a little the main body
of the boards AA should be 15 in. wide. The back, B, should be
about 22 in. long by 16 in. wide and set in between sides AA. Cut
the top, C, 16 in. long and 14-1/4 in. wide. The bottom must be
the same length as the top and 13-1/2 in. wide.

The door, D, can be made panel as shown, or a single piece, 16
in. wide and about 20 in. long. All material used is to be made
from boards that will dress to 3/4 in. thick.

Shelving may be put in as shown in Fig. 2 and made from 1/4-in.
material. Make 12 cleats, E, 13-1/2 in. long, from a strip of
wood 1/2 by 3/4 in., with a groove 1/4 by 1/4 in. cut in them.
Fasten 6 cleats evenly spaced on the inside of each of the sides,
AA, with 3/4-in. brads. This will give seven spaces for music and
as the shelves are removable two places can be made into one.

Easily Made Wireless Coherer

Detail of Coherer

A good wireless coherer may be made with very little expense, the
only materials necessary being a glass tube, two corks: a
magnetized needle and a quantity of iron and silver filings. Push
a piece of wire through one cork and place in the bottom of the
tube, as shown in the sketch.

Pour in the filings and insert the top cork with the needle
pushed through from above. The point of the needle should barely
touch the filings and by slightly agitating the tube the iron
filings will separate from the silver and cling to the magnetized
needle, as shown.

In operation, the device must stand on end and should be
connected in the circuit as shown in the sketch. When the
electrical waves strike the needle, the conductivity of the
filings is established and a click is heard in the receiver.

Contributed by Carl Formhals, Garfield, Ill.

One-Wire Telegraph Line

Diagram of One-Wire Line

The accompanying wiring diagram shows a telegraph system that
requires no switches and may be operated with open-circuit
batteries on a one-wire line with ground connections at each end.
Any telegraph set in which the key makes double contact can be
connected up in this way.

Contributed by R. A. Brown, Fairport, N. Y.

How to Make a Water Rheostat

Water Rheostat

A water rheostat may be made by fitting a brass tube with a cork,
through which a piece of wire is passed. The brass tube may be an
old bicycle hand pump, A (see sketch), filled with water. Pushing
the wire, B, down into the water increases the surface in
contact, and thus decreases the resistance. An apparatus of this
kind is suitable for regulating the current from an induction
coil, when the coil is not provided with a regulator, and by
using a piece of pipe instead of the tube, it can be used to
regulate the speed of a motor.

When the pipe is used, a piece of brass or copper rod should be
substituted for the wire, in order to increase the surface.
Adding salt to the water will decrease the resistance, and,
when used with a motor, will give a greater speed.

Contributed by John Koehler, Ridgewood, N. J.

Electric Door-Opener

Apparatus Placed on Inside of Door

Wiring Diagram

A very convenient and efficient device for unlocking any door
fitted with a spring lock is shown in the accompanying sketches.
A fairly stiff spring, A, is connected by a flexible wire cord to
the knob B. The cord is also fastened to a lever, C, which is
pivoted at D and is released by a magnetic trigger, E, made from
the armature and magnet of an old electric bell.

When the circuit is completed by means of a secret contact device
outside the door, the magnet, F, pulls down the armature, which
releases the trigger and allows the spring to open the lock. If
there are metal numbers on the outside of the door they may be
used for the secret contact, if desired, but if there are no
numbers on the door, a small contact-board may be constructed by
driving about 12 brass headed tacks into a thin piece of wood and
making connections at the back as shown in the wiring diagram.

In this particular diagram the tacks numbered 1 and 7 are used
for unlocking the door, the others being connected with the
electric-bell circuit as indicated, for the purpose of giving an
alarm should anybody try to experiment with the secret contacts.
By means of a pocket knife or other metal article the operator
can let himself in at any time by connecting the tacks numbered 1
and 7, while a person not knowing the combination would be liable
to sound the alarm. Of course, the builder of this device may
choose a combination of his own and may thus prevent anybody else
from entering the door, even those who read this description.

Contributed by Perry A. Borden, Gachville, N. B.

How to Tighten a Curtain-Roller Spring

A common table fork can be used to hold the little projection on
the end of a curtain roller for tightening the spring. Hold the
fork firmly with one hand while turning the roller with the
other. Do not let go of the fork until the little catches are set
in position to prevent the spring from turning, or else the fork
may be thrown off with dangerous force.

Alarm Clock Chicken Feeder

An automatic poultry feeder, which will discharge the necessary
amount of corn or other feed at any desired time, may be made by
using an alarm clock as shown in the sketch. A small wire trigger
rests on the winding key and supports the swinging bottom of the
food hopper by means of a piece of string which connects the two.
When the alarm goes off the trigger drops and allows the door to
open, thus discharging the contents of the hopper. After the
device has been in operation for some time the hens will run to
the feeder whenever the bell rings.

Contributed by Dr. H. A. Dobson, Washington, D. C.

Homemade Disk-Record Cabinet

Cabinet Holding 32 Records

Select some boards that have a nice grain and about 1 in. thick
and 12-in. wide. Cut the end pieces each 36-in. long and trim
down the edges so as to make them 11-3/8 in. wide. The top board
is made 28-in. long and full 12-in. wide. The three shelves are
cut 25-in. long and the edges trimmed so they will be 11-3/8 in.
wide. The distance between the bottom of the top board and the
top of the first shelf should be 3 in. Two drawers are fitted in
this space, as shown in Fig. 1. A series of grooves are cut 1/4
in. wide, 1/4 in. deep and 3/4 in. apart on one side of the top
and bottom shelves, as shown in Fig. 2, and on both sides of the
middle shelf. The shelves should be spaced 9-5/8 in. for 10-in.
records and 5-5/8 in. for 6-in. records. A neat scroll design is
cut from a board 25 in. long to fill up and finish the space
below the bottom shelf.

Contributed by H. E. Mangold, Compton, Cal.

A Battery Rheostat

Battery Rheostat

In a board 7 in. long and 5 in. wide bore holes about 1/4 in.
apart, in a semicircle 2 in. from the bottom, and cut notches in
top end to correspond with the holes. From a piece of brass a
switch, C, is cut with a knob soldered on at the end. Nails for
stops are placed at DD. Two binding-posts are placed in board at
A and B. With about 9 ft. of fine iron wire attach one end to the
bottom of post A and run through first hole and over in first
notch to back of board and then through second hole and over
second notch and so on until E is reached, where the other end of
wire is fastened. Connect switch to post B.

Contributed by Edmund Kuhn, Jr., East Orange, N. J.

Automatic Time Switch

Will Open or Close Circuit as Desired

This device may be used to either open or close the circuit at
any desired time. An alarm clock is firmly fastened to a wooden
bracket and provided with a small wood or metal drum, A, to which
is fastened a cord, B. The other end of the cord is tied to the
switch handle so that when the alarm goes off the switch is
either opened or closed, depending on whether the cord is
passed over pulley C or pulley D.

When the cord is passed over pulley C, as shown in Fig. 1, the
circuit will be closed when the alarm goes off, but if it is
passed over D the circuit will be opened. Pulley D is fastened to
a piece of spring steel, E, which in operation is bent, as shown
by the dotted lines, thus causing the switch to snap open quickly
and prevent forming an arc.

Contributed by Douglas Royer, Roanoke, Va.

How to Make a Rotary Pump

Details of Rotary Pump

A simple rotary pump is constructed on the principle of creating
a vacuum in a rubber tube and so causing water to rise to fill
the vacuum. Figs. 3, 4 and 5 show all the parts needed, excepting
the crank and tubing. The dimensions and description given are
for a minimum pump, but a larger one could be built in
proportion.

Through the center of a block of wood 4 in. square and 7/8 in.
thick (A, Figs. 1, 2 and 3) saw a circular opening 2-7/8 in. in
diameter. On each side of this block cut a larger circle 3-1/4
in. in diameter, having the same center as the first circle (Fig.
3). Cut the last circles only 1/4 in. deep, leaving the first
circle in the form of a ridge or track 3/8 in. wide, against
which the rubber tubing, E, is compressed by wheels. Bore two 1/4
in. holes (HH, Fig. 1) from the outside of the block to the edge
of the inner circle. Put the rubber tube, E, through one of these
holes, pass it around the track and out through the other hole.
Notice the break (S) in the track; this is necessary in order to
place in position the piece holding the wheels.

Fig. 4 shows the wheel-holder, B. Make it of hard wood 3-1/8 in.
long, 1 in. wide and a little less than 7/8 in. thick, so that it
will run freely between the sides (Fig. 5) when they are placed.
Cut two grooves, one in each end, 1 in. deep and 1/2 in. wide. In
these grooves place wheels, CC, to turn on pins of stout wire.
These wheels should be 3/4 in. in diameter. When placed in the
holder their centers must be exactly 2 in. apart, or so arranged
that the distance between the edge of the wheels and the track
(K, Fig. 1) is equal to the thickness of the tubing when pressed
flat. If the wheels fit too tightly, they will bind; it too
loose, they will let the air through. Bore a hole through the
middle of the wheel-holder and insert the crankpin, D, which
should be about 1/2 in. in diameter. The crankpin should fit
tightly; if necessary drive a brad through to keep it from
slipping.

In the sides (Fig. 5) bore a hole in the center of the crankpin
to run in loosely. Now put all these parts together, as shown in
the illustration. Do not fasten the sides too securely until you
have tried the device and are sure it will run smoothly. For the
crank a bent piece of stout wire or a nail will serve, though a
small iron wheel is better, as it gives steadiness to the motion.
In this case a handle must be attached to the rim of the wheel to
serve as a crank. The drive wheel from a broken-down eggbeater
will do nicely. For ease in handling the pump, a platform should
be added.

To use the pump, fill the tube with water and place the lower end
of the tube in a reservoir of water. Make a nozzle of the end of
a clay pipe stem for the other end of the tube. Then turn the
crank from left to right. The first wheel presses the air out of
the tube, creating a vacuum which is immediately filled with
water. Before the first wheel releases the tube at the top, the
other wheel has reached the bottom, this time pressing along the
water that was brought up by the first wheel. If the motion of
the wheels is regular, the pump will give a steady stream. Two
feet of 1/4-in. tubing, costing 10 cents, is all the expense
necessary.

Contributed by Dan H. Hubbard, Idana, Kan.

How to Make a Fire Screen

Fig. 1
Fig. 2 Made of Strap Iron

A screen which will not interfere with the radiation of the heat
from the fire, and will keep skirts and children safe can be made
at little expense out of some strap iron. The screen which is
shown in Fig. 1, stands 20 in. high from the base to the top
cross-piece and is made of 3/4 by 1/4-in. and 1/2 by 1/4-in.
iron. The top and bottom pieces marked AA, Fig. 1, are 3/4 by 1/4
in. and are 30 in. long, bent at an angle to fit the fireplace 7
in. from each end, as shown in Fig. 2. The three legs marked BBB,
Fig. 1, are of the same size iron and each leg will take 34 in.
of material. In shaping the feet of these three pieces give them
a slight tendency to lean toward the fire or inside of screen,
says a correspondent in the Blacksmith and Wheelwright. In the
two cross bars 1 in. from each end, A in Fig. 2, mark for hole
and 3 in. from that mark the next hole. Take the center of the
bar, B, 15 in. from each end, and mark for a hole, and 3-1/2 in.
on each side mark again and 3-1/2 in. beyond each of these two,
mark again.

Mark the legs 2-3/4 in. from the bottom and 2 in. from the top
and after making rivet-holes rivet them to the cross bars, AA,
Fig. 1.

Cut six pieces, 17-1/2 in. long and punch holes to fit and rivet
onto the remaining holes in cross bars, AA, Fig. 1. Clean it up
and give it a coat of black Japan or dead black.

Trap for Small Animals

This is a box trap with glass sides and back, the panes of glass
being held in place by brads placed on both sides. The animal
does not fear to enter the box, because he can see through it:
when he enters, however, and touches the bait the lid is released
and, dropping, shuts him in. This is one of the easiest traps to
build and is usually successful.

Homemade Grenet Battery

Fig.1 Details of Homemade Battery

Procure an ordinary carbon-zinc, sal-ammoniac battery and remove
the zinc rod. If the battery has been used before, it is better
to soak the carbon cylinder for a few hours to remove any
remaining crystals of sal-ammoniac from its pores.

The truncated, conical zinc required is known as a fuller’s zinc
and can be bought at any electrical supply dealer’s, or, it may
be cast in a sand mold from scrap zinc or the worn-out zinc rods
from sal-ammoniac batteries. It should be cast on the end of a
piece of No. 14 copper wire. Amalgamation is not necessary for
the zinc one buys, but if one casts his own zinc, it is necessary
to amalgamate it or coat it with mercury. This may be done as
follows:

Dip a piece of rag in a diluted solution of sulphuric acid (water
16 parts, acid 1 part); rub the zinc well, at the same time
allowing a few drops of mercury
to fall on a spot attacked by the
acid. The mercury will adhere,
and if the rubbing is continued so
as to spread the mercury,
it will cover the entire surface of the
zinc, giving it a bright, silvery appearance.

Next procure what is known as a wire connector. This is a piece
of copper tube about 1-1/2 in. long having two thumb screws, one
on each end on opposite sides (Fig. 2). The upper screw is to
connect the battery wire, the lower one to raise and lower the
zinc. The battery is now complete, and the solution (Fig. 1) must
be prepared. Proceed as follows:

In 32 oz. of water dissolve 4 oz. potassium bichromate. When the
bichromate has all dissolved, add slowly, stirring constantly, 4
oz. sulphuric acid.
Do not add the acid too quickly or the heat
generated may break the vessel containing the solution. Then pour
the solution into the battery jar, until it is within 3 in. of
the top. Thread the wire holding the zinc through the porcelain
insulator of the carbon cylinder and also through the wire
connector. Pull the zinc up as far as it will go and tighten the
lower thumb screw so that it holds the wire secure. Place the
carbon in the jar. If the solution touches the zinc, some of it
should be poured out. To determine whether or not the zinc is
touched by the solution, take out the carbon and lower the zinc.
If it is wet, there is too much liquid in the jar. The battery is
now ready for use.

To cause a flow of electricity, lower the zinc until it almost
touches the bottom of the jar and connect an electric bell or
other electrical apparatus by means of wires to the two binding
posts.

This battery when first set up gives a current of about two
volts. It is useful for running induction coils, or small
electric motors. When through using the battery, raise the zinc
and tighten the lower thumb screw. This prevents the zinc wasting
away when no current is being used.

Contributed by H. C. Meyer, Philadelphia.

Door-Opener for Furnace

Furnace Door Opener

The accompanying diagram shows an arrangement to open the coal
door of a furnace. When approaching the furnace with a shovelful
of coal it is usually necessary to rest the shovel on the top of
the ash door, while the coal door is being opened. With my device
it is only necessary to press the foot pedal, which opens the
door. After putting in the coal, pressing the pedal closes the
door. The pulley in the ceiling must be placed a little in front
of the door, in order to throw the door open after lifting it
from the catch. A large gate hinge is used to hold the pedal to
the floor.

Contributed by Edward Whitney, Madison, Wis.

How to Make an Efficient Wireless Telegraph
By George W. Richardson

A simple but very efficient wireless telegraph may be constructed
at slight cost from the following description:

The sending apparatus consists of nothing but an induction coil
with a telegraph key inserted in the primary circuit, i. e., the
battery circuit. This apparatus may be purchased from any
electrical-supply house. The price of the coil depends upon its
size, and upon the size depends the distance signals can be
transmitted. If, however, one wishes to construct his own coil he
can make and use, with slight changes, the jump-spark coil
described elsewhere in this book. This coil, being a 1-in. coil,
will transmit nicely up to a distance of one mile; while a 12-in.
coil made on the same plan will transmit 20 miles or even more
under favorable conditions.

Change the coil described, as follows: Insert an ordinary
telegraph key in the battery circuit, and attach two small pieces
of wire with a brass ball on each, by inserting them in the
binding-posts of the coil as shown at B B”. Of these two terminal
wires one is grounded to earth, while the other wire is sent
aloft and is called the aerial line. This constitutes all there
is to the sending apparatus. Now for the receiving apparatus. In
the earlier receiving instruments a coherer was used, consisting
of a glass tube about 1/8-in. diameter, in which were two silver
pistons separated by nickel and silver filings, in a partial
vacuum. This receiver was difficult of adjustment and slow in
transmission. An instrument much less complicated and inexpensive
and which will work well can be made thus:

Take a 5-cp. incandescent lamp and break off the tip at the
dotted line, as shown in Fig. 5. This can be done by giving the
glass tip or point a quick blow with a file or other thin edged
piece of metal. Then with a blow-torch heat the broken edges
until red hot and turn the edges in as seen in Fig. 6. Remove the
carbon filament in the lamp and bend the two small platinum wires
so they will point at each other as in Fig. 6, W W. Screw the
lamp into an ordinary wall socket which will serve as a base as
in Fig. 7. Make a solution of 1 part
sulphuric acid to 4 parts of
water, and fill the lamp about two-thirds full (Fig. 7). This
will make an excellent receiver. It will be necessary to adjust
the platinum points, W W, to suit the distance the message is to
be worked. For a mile or less the points should be about 1/16 in.
apart, and closer for longer distances.

The tuning coil is simply a variable choking coil, made of No. 14
insulated copper wire wound on an iron core, as shown in Fig. 7.
After winding, carefully scrape the insulation from one side of
the coil, in a straight line from top to bottom, the full length
of the coil, uncovering just enough to allow a good contact for
the sliding piece. The tuning is done by sliding the contact
piece, which is made of light copper wire, along the convolutions
of the tuning coil until you can hear the signals. The signals
are heard in a telephone receiver, which is shown connected in
shunt across the binding posts of the lamp holder with one or two
cells of dry battery in circuit, Fig.7.

The aerial line, No.6 stranded, is run from binding-post B
through the choking or tuning coil, and for best results should
extend up 50 ft. in the air. To work a 20-mile distance the line
should be 100 or 150 ft. above the ground. A good way is to erect
a wooden pole on a house or barn and carry the aerial wire to the
top and out to the end of a gaff or arm.

To the end of the aerial wire fasten a bunch of endless loops
made of about No. 14 magnet wire (bare or insulated), attaching
both ends to the leading or aerial wire. The aerial wire should
not come nearer than 1 ft. at any point to any metal which is
grounded.

Run a wire from the other binding post, A, to the ground and be
sure to make a good ground connection.

For simple experimental work on distances of 100 ft. only, an
ordinary automobile spark coil can be used in place of the more
elaborate coil, Figs. 1 to 4.

The above-mentioned instruments have no patents on them, and
anyone is at liberty to build and use them. The writer does not
claim to be the originator, but simply illustrates the above to
show that, after all, wireless is very simple when it is once
understood. The fundamental principles are that induction travels
at right angles, 90°, to the direction of the current. For an
illustration, if a person standing on a bridge should drop a
pebble into the water below, after contact he would note circles
radiating out over the surface of the water. These circles, being
at right angles, 90°, to the direction of the force that caused
the circles, are analogous to the flow of induction, and hence
the aerial line, being vertical, transmits signals horizontally
over the earth’s surface.

Beeswax for Wood Filler

When filling nail holes in yellow pine use beeswax instead of
putty, as it matches the color well.

How to Make a Lathe

Assembled Lathe Bed and Bearing Details

FIG. 6 Headstock Details

FIG.7 Details of Tailstock

A small speed-lathe, suitable for turning wood or small metal
articles, may be easily made at very little expense. A lathe of
this kind is shown in the cut (Fig. 1), where A is the headstock,
B the bed and C the tailstock. I run my lathe by power, using an
electric motor and countershaft, but it could be run by foot
power if desired. A large cone pulley would then be required, but
this may be made in the same manner as the small one, which will
be described later.

The bed of the machine is made of wood as shown in Figs. 2 and 3,
hardwood being preferable for this purpose. Fig. 2 shows an end
view of the assembled bed, and Fig. 3 shows how the ends are cut
out to receive the side pieces.

The headstock, Fig. 6, is fastened to the bed by means of
carriage bolts, A, which pass through a piece of wood, B, on the
under side of the bed. The shaft is made of 3/4-in. steel tubing
about 1/8 in. thick, and runs in babbitt bearings, one of which
is shown in Fig. 5.

To make these bearings, cut a square hole in the wood as shown,
making half of the square in each half of the bearing. Separate
the two halves of the bearing slightly by placing a piece of
cardboard on each side, just touching the shaft. The edges which
touch the shaft should be notched like the teeth of a saw, so as
to allow the babbitt to run into the lower half of the bearing.
The notches for this purpose may be about 1/8 in. pitch and 1/8
in. deep. Place pieces of wood against the ends of the bearing as
shown at A and B, Fig. 4, and drill a hole in the top of the
bearing as shown in Fig. 4.

The bearing is then ready to be poured. Heat the babbitt well,
but not hot enough to burn it, and it is well to have the shaft
hot, too, so that the babbitt will not be chilled when it strikes
the shaft. If the shaft is thoroughly chalked or smoked the
babbitt will not stick to it. After pouring, remove the shaft and
split the bearing with a round, tapered wooden pin. If the
bearing has been properly made, it will split along the line of
the notched cardboard where the section of the metal is smallest.
Then drill a hole in the top as shown at A, Fig. 5, drilling just
deep enough to have the point of the drill appear at the lower
side. This cavity acts as an oil cup and prevents the bearing
from running dry.

The bolts B (Fig. 5) are passed through holes in the wood and
screwed into nuts C, which are let into holes D, the holes
afterward being filled with melted lead.
This type of bearing will be found very satisfactory and may be
used to advantage on other machines. After the bearings are
completed the cone pulley can be placed on the shaft. To make
this pulley cut three circular pieces of wood to the dimensions
given in Fig. 6 and fasten these together with nails and glue. If
not perfectly true, they may be turned up after assembling, by
rigging up a temporary toolrest in front of the headstock.

The tail stock (Fig. 7) is fastened to the bed in the same manner
as the headstock, except that thumb nuts are used on the carriage
bolts, thus allowing the tail stock to be shifted when necessary.
The mechanism of the center holder is obtained by using a l/2-in.
pipe, A, and a 1/2-in. lock nut, B, embedded in the wood.

I found that a wooden tool-rest was not satisfactory, so I had to
buy one, but they are inexpensive and much handier than homemade
tool rest.

Contributed by Donald Reeves, Oak Park, Ill.

To Use Old Battery Zincs

Showing Zinc Suspended

When the lower half of a battery zinc becomes eaten away the
remaining part can be used again by suspending it from a wire as
shown in the cut. Be sure and have a good connection at the zinc
binding post and cover that with melted paraffin. This prevents
corrosion, which would otherwise occur from the action of the sal
ammoniac or other chemical. The wire may be held at the top by
twisting it around a piece of wood or by driving a peg through
the hole in the porcelain insulator.

Contributed by Louis Lauderbach, Newark, N.J.

Callers’ Approach Alarm

Alarm Rings When Caller Approaches

This alarm rings so that callers approaching the door may be seen
before they ring the bell and one can exercise his pleasure about
admitting them.

If one has a wooden walk, the alarm is easy to fix up. Take up
about 5 ft. of the walk and nail it together so as to make a
trapdoor that will work easily. Place a small spring under one
end to hold it up about 1/4 in. (A, Fig. 2). Nail a strip of tin
along the under side of the trap near the spring and fasten
another strip on the baseboard, so that they will not touch, save
when a weight is on the trap. Connect up an electric bell,
putting the batteries and bell anywhere desired, and using
rubber-covered wire outside the house, and the alarm is complete.

When a person approaching the house steps on the trap, the bell
will ring and those in the house can see who it is before the
door bell rings.

Contributed by R. S. Jackson, Minneapolis, Minn.

Easy Method of Electroplating

Electroplating Apparatus

Before proceeding to electroplate with copper, silver or other
metal, clean the articles thoroughly, as the least spot of grease
or dirt will prevent the deposit from adhering. Then polish the
articles and rub them over with a cloth and fine pumice powder,
to roughen the surface slightly. Finally, to remove all traces of
grease, dip the articles to be plated in a boiling potash
solution made by dissolving 4 oz. American ash in 1-1/2 pt. of
water. Do not touch the work with the hands again. To avoid
touching it, hang the articles on the wires, by which they are to
be suspended in the plating bath, before dipping them in the
potash solution; then hold them by the wires under running water
for ten minutes to completely remove every trace of the potash.

For plating with copper prepare the following solution: 4 oz.
copper sulphate dissolved in 12 oz. water; add strong ammonia
solution until no more green crystals are precipitated. Then add
more ammonia and stir until the green crystals are redissolved
giving an intense blue solution. Add slowly a strong solution of
potassium cyanide
until the blue color disappears, leaving a
clear solution; add potassium cyanide
again, about one-fourth as
much in bulk as used in the decolorizing process. Then make the
solution up to 2 qt. with water. With an electric pressure of 3.5
to 4 volts, this will give an even deposit of copper on the
article being plated.

A solution for silver plating may be prepared as follows:
Dissolve 3/4 oz. of commercial silver nitrate in 8 oz. of water,
and slowly add a strong solution of
potassium cyanide until no
more white precipitate is thrown down. Then pour the liquid off
and wash the precipitate carefully. This is best done by filling
the bottle with water, shaking, allowing precipitate to settle
and then pouring off the water. Repeat six times. Having finished
washing the precipitate, slowly add to it a solution of
potassium cyanide
until all the precipitate is dissolved. Then add an
excess of potassium cyanide—about
as much as was used in dissolving the precipitate—and make the
solution up to 1 qt. with water. This solution, with an electric
pressure of 2 to 4 volts, will give a good white coat of silver
in twenty minutes to half-an-hour; use 2 volts for large
articles, and 4 volts for very small ones. If more solution is
required, it is only necessary to double all given quantities.

Before silver plating, such metals as iron,
lead, pewter, zinc,
must be coated with copper in the alkaline copper bath described,
and then treated as copper. On brass, copper, German silver,
nickel and such metals, silver can be plated direct. The deposit
of silver will be dull and must be polished. The best method is
to use a revolving scratch brush; if one does not possess a
buffing machine, a hand scratch brush is good. Take quick, light
strokes. Polish the articles finally with ordinary plate powder.

The sketch shows how to suspend the articles in the plating-bath.
If accumulators are used, which is advised, be sure to connect
the positive (or red) terminal to the piece of silver hanging in
the bath, and the negative (or black) terminal to the article to
be plated. Where Bunsen cells are used, the carbon terminal takes
the place of the positive terminal of the accumulator.

Model Engineer.

An Ingenious Electric Lock for a Sliding Door

Electric Lock for Sliding Door

The apparatus shown in Fig. 1 not only unlocks, but opens the
door, also, by simply pressing the key in the keyhole.

In rigging it to a sliding door, the materials required are:
Three flat pulleys, an old electric bell or buzzer, about 25 ft.
of clothesline rope and some No. 18 wire. The wooden catch, A
(Fig. 1), must be about 1 in. thick and 8 in. long; B should be
of the same wood, 10 in. long, with the pivot 2 in. from the
lower end. The wooden block C, which is held by catch B, Can be
made of a 2-in. piece of broomstick. Drill a hole through the
center of this block for the rope to pass through, and fasten it
to the rope with a little tire tape.

When all this is set up, as shown in Fig. 1, make a key and
keyhole. A 1/4 in. bolt or a large nail sharpened to a point, as
at F, Fig. 3, will serve for the key. To provide the keyhole, saw
a piece of wood, I, 1 in. thick by 3 in. square, and bore a hole
to fit the key in the center. Make a somewhat larger block (E,
Fig. 3) of thin wood with a 1/8-in. hole in its center. On one
side of this block tack a piece of tin (K, Fig. 3) directly over
the hole. Screw the two blocks together, being careful to bring
the holes opposite each other. Then, when the point of the key
touches the tin, and the larger part (F, Fig. 3) strikes the bent
wire L, a circuit is completed; the buzzer knocks catch A (Fig.
1), which rises at the opposite end and allows catch B to fly
forward and release the piece of broomstick C. The weight D then
falls and jerks up the hook-lock M, which unlocks the door, and
the heavier weight N immediately opens it.

Thus, with a switch as
in Fig. 3, the door can only be opened by the person who has the
key, for the circuit cannot be closed with an ordinary nail or
wire. B, Fig. 2, shows catch B, Fig. 1, enlarged; O, Fig. 2, is
the cut through which the rope runs; H, Fig. 1, is an elastic
that snaps the catch back into place, and at G the wires run
outside to the keyhole.

This arrangement is very convenient when one is carrying
something in one hand and can only use the other. Closing the
door winds up the apparatus again.

Contributed by E. H. Klipstein, 116 Prospect St., East Orange, New Jersey.

Parlor Magic for Winter Evenings
By C. H. CLAUDY

The Magic Cave

You are seated in a parlor at night, with the lights turned low.
In front of you, between the parlor and the room back of it, is
an upright square of brightly burning lights, surrounding a
perfectly black space. The magician stands in front of this, in
his shirt sleeves, and after a few words of introduction proceeds
to show the wonders of his magic cave. Showing you plainly that
both hands are empty, he points with one finger to the box, where
immediately appears a small white china bowl. Holding his empty
hand over this bowl, some oranges and apples drop from his empty
hand into the bowl. He removes the bowl from the black box, or
cave, and hands its contents round to the audience. Receiving the
bowl again, he tosses it into the cave, but it never reaches the
floor—it disappears in midair.

The illusions he shows you are too many to retail at length.
Objects appear and disappear. Heavy metal objects, such as forks,
spoons and jackknives, which have been shown to the audience and
which can have no strings attached to them, fly about in the box
at the will of the operator. One thing changes to another and
back again, and black art reigns supreme.

Now all this “magic” is very simple and requires no more skill to
prepare or execute than any clever boy or girl of fourteen may
possess. It is based on the performance of the famous Hermann,
and relies on a principle of optics for its success. To prepare
such a magic cave, the requisites are a large soap box, a few
simple tools, some black paint, some black cloth, and plenty of
candles.

The box must be altered first. One end is removed, and a slit,
one-third of the length from the remaining end, cut in one side.
This slit should be as long as the width of the box and about
five inches wide. On either side of the box, half way from open
end to closed end, should be cut a hole, just large enough to
comfortably admit a hand and arm.

Next, the box should be painted black both inside and out, and
finally lined inside with black cloth. This lining must be done
neatly-no folds must show and no heads of tacks. The interior
must be a dead black. The box is painted black first so that the
cloth used need not be very heavy; but if the cloth be
sufficiently thick, no painting inside is required. The whole
inside is to be cloth-lined, floor, top, sides and end.

Next, the illumination in front must be arranged. If you can have
a plumber make you a square frame of gas-piping, with tiny holes
all along it for the gas to escape and be lit, and connect this
by means of a rubber tube to the gas in the house, so much the
better; but a plentiful supply of short candles will do just as
well, although a little more trouble. The candles must be close
together and arranged on little brackets around the whole front
of the “cave” (see small cut), and should have little pieces of
bright tin behind them, to throw the light toward the audience.
The whole function of these candles is to dazzle the eyes of the
spectators, heighten the illusion, and prevent them seeing very
far into the black box.

Finally, you must have an assistant, who must be provided with
either black gloves or black bags to go over his hands and arms,
and several black drop curtains, attached to sticks greater in
length than the width of the box, which are let down through the
slit in the top.

The audience room should have only low lights; the room where the
cave is should be dark, and if you can drape portieres between
two rooms around the box (which, of course, is on a table) so
much the better.

The whole secret of the trick lies in the fact that if light be
turned away from anything black, into the eyes of him who looks,
the much fainter light reflected from the black surface will not
affect the observer’s eye. Consequently, if, when the exhibitor
puts his hand in the cave, his confederate behind inserts his
hand, covered with a black glove and holding a small bag of black
cloth, in which are oranges and apples, and pours them from the
bag into a dish, the audience sees the oranges and apples appear,
but does not see the black arm and bag against the black
background.

The dish appears by having been placed in position behind a black
curtain, which is snatched swiftly away at the proper moment by
the assistant. Any article thrown into the cave and caught by the
black hand and concealed by a black cloth seems to disappear.
Any object not too large can be made to “levitate” by the same
means. A picture of anyone present may be made to change into a
grinning skeleton by suddenly screening it with a dropped
curtain, while another curtain is swiftly removed from over a
pasteboard skeleton, which can be made to dance either by
strings, or by the black veiled hand holding on to it from
behind, and the skeleton can change to a white cat.

But illusions suggest themselves. There is no end to the effects
which can be had from this simple apparatus, and if the operators
are sufficiently well drilled the result is truly remarkable to
the uninitiated. The illusion, as presented by Hermann, was
identical with this, only he, of course, had a big stage, and
people clothed in black to creep about and do his bidding, while
here the power behind the throne is but a black-veiled hand and
arm. It can be made even more complicated by having two
assistants, one on each side of the box, and this is the reason
why it was advised that two holes be cut. This enables an
absolutely instantaneous change as one uncovers the object at the
moment the second assistant covers and removes the other.

It is important that the assistants remain invisible throughout,
and if portieres are impossible, a screen must be used. But any
boy ingenious enough to follow these simple instructions will not
need to be told that the whole success of the exhibition depends
upon the absolute failure of the audience to understand that
there is more than one concerned in bringing about the curious
effects which are seen. The exhibitor should be a boy who can
talk; a good “patter”—as the magicians call it—is often of
more value than a whole host of mechanical effects and helpers.
It is essential that the exhibitor and his confederate be well
drilled, so that the latter can produce the proper effects at
the proper cue from the former. Finally, never give an exhibition
with the “cave” until you have watched the illusions from the
front yourself; so that you can determine whether everything
connected with the draping is right, or whether some stray bit of
light reveals what you wish to conceal.

Reversing-Switch for Electrical Experiments

Fig. 2 Suitable for Students’ Use

A homemade reversing-switch, suitable for use by students of
electrical and engineering courses in performing experiments, is
shown in the diagram.

Referring to Fig. 1, A represents a pine board 4 in. by 4 in. and
a is a circular piece of wood about 1/4 in. square, with three
brass strips, b1, b2, b3, held down on it by two terminals, or
binding posts, c1, c2, and a common screw, d. Post c1 is
connected to d by means of an insulated wire, making them carry
the same kind of current (+ in the sketch).

About the center piece H moves a disk, held down by another disk
F (Fig. 2), which is fastened through the center piece to the
wooden base, A, by means of two wood screws. On the disk G are
two brass strips, e1 and e2, so arranged that, when handle K is
turned to one side, their one end just slips under the strips b1,
b2, or b2, b3, respectively, making contact with them, as shown
in Fig. 2, at L, while their other ends slide in two
half-circular brass plates f1, f2, held down on disk F by two
other terminals, c3, c4, making contact with them as shown at y,
Fig. 2.

The action of the switch is shown in Fig. 1. Connect terminal c1
to the carbon of a battery, and c2 to the zinc. Then, if you turn
handle K to the right, so that the strips e1 and e2 touch b1 and
b2, respectively, terminal c3 will show +, and c1 – electricity;
vice versa, if you turn the handle to the left so that e1 and e2
touch b2 and b3, respectively, terminal c3 will show – , and c4 +
electricity. The switch is easy to make and of very neat
appearance.

How to Receive Wireless Telegraph Messages with a Telephone

Wiring Diagram for Wireless Telegraph

Any telephone having carbon in the transmitter (all ordinary
telephones have carbon transmitters) can be used to receive
wireless messages by simply making a few changes in the
connections and providing a suitable antenna. Connect the
transmitter and receiver in series with three dry cells and run
one wire from the transmitter to the antenna. Connect the other
transmitter wire to a water or gas pipe in order to ground it,
and then hold the receiver to your ear. Any wireless telegraph
message within a radius of one mile will cause the transmitter to
act as a coherer, thus making the message audible in the
receiver.

By using an ordinary telephone transmitter and receiver and a
1/2-in. jump spark coil, a complete wireless telegraph station
may be made, which will send or receive messages for a radius of
one mile. The accompanying wiring diagram shows how to make the
connections. By putting in an extra switch three of the sending
batteries may be switched in when receiving, thus obviating the
necessity of an extra set of batteries.

Contributed by A. E. Joerin.

Connecting Up Batteries to Give Any Voltage

Referring to the illustration: A is a five-point switch (may be
homemade); B is a one-point switch, and C and C1 are binding
posts. When switch B is closed and A is on No. 1, you have the
current of one battery; when A is on No. 2 you receive the
current from two batteries; when on No. 3, from three batteries;
when on No. 4, from four batteries, and when on No. 5, from five
batteries. More batteries may be connected to each point of
switch B.

I have been using the same method for my water rheostat
(homemade). I have the jars of water where the batteries are and
the current coming in at a and b.

Contributed by Eugene F. Tuttle, Jr., Newark, Ohio.

A Simple Accelerometer

A simple accelerometer for indicating the increase in speed of a
train was described by Mr. A. P. Trotter in a paper read before
the Junior Institution of Engineers of Great Britain. The device
consists of an ordinary 2-ft. rule, A, with a piece of thread
tied to the 22-in. mark, as shown in the sketch, and supporting
the small weight, B, which may be a button or other small object.

The device thus arranged, and placed on the windowsill of the
car, will indicate the acceleration and retardation as follows:
Every 1/2 in. traveled by the thread, over the bent portion of
the rule, indicates an increase of or decrease of velocity to the
extent of 1 ft. per second for each second. Thus, it the thread
moved 2-1/4 in. in a direction opposite to the movement of the
train, then the train would be increasing its speed at the rate
of 4-1/2 ft. per second.

If the thread is tied at the 17-in. mark, then each half inch
will represent the mile per hour increase for each second. Thus
if the thread moves 1 in., it shows that the train is gaining 2
miles an hour each second.

An Egg-Shell Funnel

Bottles having small necks are hard to fill without spilling the
liquid. A funnel cannot be used in a small opening, and pouring
with a graduate glass requires a steady hand. When you do not
have a graduate at hand, a half egg-shell with a small hole
pricked in the end will serve better than a funnel. Place the
shell in an oven to brown the surface slightly and it will be
less brittle and last much longer.

Contributed by Maurice Baudier, New Orleans, La.

Handy Electric Alarm

Handy Electric Alarm

An electric alarm which one may turn off from the bed without
arising combined with a light which may be turned on and off from
a lying position, so one can see the time, is the device of H. E.
Redmond, of Burlington, Wis.

The alarm clock rests on a shelf, A, which has a piece of metal,
B, fastened in such a position that the metal rod C, soldered to
the alarm winder, will complete the circuit and ring the bell.
The two-point switch D is closed normally at E, but may be
closed at F any time desired, thus turning on the small
incandescent light G, which illuminates the face of the clock.
When the alarm goes off, the bell will continue to ring until the
switch is opened.

To Keep Dogs and Cats Away from the Garbage-Can

Last summer I was annoyed a great deal by dogs upsetting our
garbage can on the lawn, but finally executed a plan that rid the
yard of them in one afternoon.

I first secured a magneto out of an old telephone, then drove a
spike in a damp place under the porch, attached a wire to the
spike and ran the wire to one of the poles of the magneto. Then I
set the garbage-can on some blocks of wood, being careful not to
have it touch the ground at any point. I next ran a wire from the
other pole of the magneto to the can, wrapping the wire around
the can several times. Then I sat down on the porch to wait.

It was not long before a big greyhound came along, putting his
forepaws on the top of the can to upset it. At the same instant I
gave the magneto a quick turn, which sent the dog away a very
surprised animal. This was repeated several times during the
afternoon with other dogs, and with the same result.

Contributed by Gordon T. Lane, Crafton, Pa.

How to Cross a Stream on a Log

When crossing a water course on a fence rail or small log, do not
face up or down the stream and walk sideways, for a wetting is
the inevitable result. Instead, fix the eye on the opposite shore
and walk steadily forward. Then if a mishap comes, you will fall
with one leg and arm encircling the bridge.

C. C. S.

Relay Made from Electric Bell

It is not necessary to remove the adjusting-screw when changing
an electric bell into a relay. Simply twist it around as at A and
bend the circuit-breaking contact back as shown. It may be
necessary to remove the head of the screw, A, to prevent
short-circuiting with the armature.

Contributed by A. L. Macey, New York City.

Foundry Work at Home

Fig. 1—Convenient Arrangement of Bench and Tools

The Equipment

Many amateur mechanics who require small metal castings in their
work would like to make their own castings. This can easily be
done at home without going to any great expense, and the variety
and usefulness of the articles produced will make the equipment a
good investment.

With the easily made devices about to be described, the young
mechanic can make his own telegraph keys and sounders, battery
zincs, binding posts, engines, cannons, bearings, small machinery
parts, models and miniature objects, ornaments of various kinds,
and duplicates of all these, and many other interesting and
useful articles.

The first thing to make is a molding bench, as shown in Fig. 1.
It is possible to make molds without a bench, but it is a mistake
to try to do this, as the sand is sure to get on the floor,
whence it is soon tracked into the house. The bench will also
make the operation of molding much easier and will prove to be a
great convenience.

The bench should be made of lumber about 1 in. thick and should
be constructed in the form of a trough, as shown. Two cleats, AA,
should be nailed to the front and back to support the
cross-boards, BE, which in turn support the mold while it is
being made. The object of using the cleats and removable
cross-boards instead of a stationary shelf is to give access to
the sand, C, when it is being prepared.

About one or two cubic feet of fine molding-sand will be
required, which may, be purchased at the nearest foundry for a
small sum. Yellow sand will be found a little better for the
amateur’s work than the black sand generally used in most
foundries, but if no yellow sand can be obtained the black kind
will do. If there is no foundry near at hand, try using sand from
other sources, giving preference to the finest sand and that
which clings together in a cake when compressed between the
hands. Common lake or river sand is not suitable for the purpose,
as it is too coarse and will not make a good mold.

For mixing and preparing the sand a small shovel, D, and a sieve,
E, will be required. If desired the sieve may be homemade.
Ordinary wire netting such as is used in screen doors, is about
the right mesh, and this, nailed to replace the bottom of a box,
makes a very good sieve.

The rammer, F, is made of wood, and is wedge-shaped at one end
and flat at the other, as shown. In foundries each molder
generally uses two rammers, but for the small work which will be
described one will be sufficient. An old teaspoon, G, will be
found useful in the molding operations and may be hung on the
wall or other convenient place when not in use.

The cloth bag, H, which can be made of a knitted stocking, is
filled with coal dust; which is used for a parting medium in
making the molds. Take a small lump of soft coal and reduce to
powder by pounding. Screen out all the coarse pieces and put the
remainder in the bag. A slight shake of the bag over the mold
will then cause a cloud of coal-dust to fall on it, thus
preventing the two layers of sand from sticking, but this
operation will be described more fully later on.

Fig. 2—Homemade Flask

The flask, J, Fig. 1, is shown more clearly in Fig. 2. It is made
of wood and is in two halves, the “cope,” or upper half, and the
“drag,” or lower part. A good way to make the flask is to take a
box, say 12 in. by 8 in. by 6 in. high, and saw it in half
longitudinally, as shown. If the box is not very strong, the
corners should be braced with triangular wooden strips, A A,
which should be nailed in, previous to sawing. The wooden strips
BB are used to hold the sand, which would otherwise slide out of
the flask when the two halves of the mold are separated.

The dowels, CC, are a very important part of the flask as upon
them depends the matching of the two halves of the mold. A
wedge-shaped piece, CC, is nailed to each end of the cope, and
the lower pieces, DD, are then nailed on the drag so that they
just touch C when the flask is closed. The two halves of the
flask will then occupy exactly the same relative position
whenever they are put together.

After the flask is done make two boards as shown at K, Fig. 1, a
little larger than the outside of the flask. A couple of cleats
nailed to each board will make it easier to pick up the mold when
it is on the floor.

A cast-iron glue-pot makes a very good crucible for melting the
metal, which can be either aluminum, white metal, zinc or any
other metal having a low melting-point. This completes the
equipment with the exception of one or two simple devices which
will now be described.

II—How to Make a Mold

Having finished making the flask and other equipment, as
described, everything will be ready for the operation of molding.
It would be well for those who have never had any experience in
this line to visit a small brass foundry, where they can watch
the molders at work, as it is much easier to learn by
observation; but they must not expect to make a good mold at the
first trial. The first attempt usually results in the sand
dropping out of the cope when it is being lifted from the drag,
either because of insufficient ramming around the edges or
because the sand is too dry.

A good way to tell when the sand is moist enough is to squeeze it
in the hand. If it forms into a cake and shows all the
finger-marks, it has a sufficient amount of moisture, but if it
crumbles or fails to cake it is too dry. An ordinary watering-pot
will be found useful in moistening the sand, but care should be
taken not to get it too wet, or the hot metal coming in contact
with it when the mold is poured will cause such rapid evaporation
that the mold will “boil” and make a poor casting. A little
practice in this operation will soon enable the molder to
determine the correct amount of moisture.

When molding with sand for the first time it will be necessary to
screen it all before using it, in order to remove the lumps, and
if water is added, the sand should be thoroughly shoveled until
the moisture is evenly distributed. The sand is then ready for
molding.

Fig. 3—Making a Mold

The operation of making a mold is as follows: The lower half of
the flask, or “drag,” and the pattern to be molded are both
placed on the cover board as shown at A. A quantity of sand
sufficient to completely cover the pattern is then sifted into
the drag, which is then filled level with the top with unscreened
sand. This is rammed down slightly with the rammer, and then more
sand is added until it becomes heaped up as shown at B. It is
then rammed again as before.

It is impossible to describe just how hard a mold should be
rammed, but by observing the results the beginner can tell when a
mold is too hard or too soft, and thus judge for himself. If the
sand falls out of the flask when lifting the cope, or if it opens
up or spreads after it is poured, it shows that the mold has been
rammed too little, and if the surface of the sand next to the
pattern is cracked it shows that the mold has been rammed too
hard. It will be found that the edges of the mold can stand a
little more ramming than the middle. In finishing the ramming,
pound evenly all over the surface with the blunt end of the
rammer.

After ramming, scrape off the surplus sand with a straight-edged
stick, as shown at C, and scatter about 1/16 in. of loose sand
over the surface for a good bearing. Place another cover board on
top, as shown at D, and by grasping with both hands, as shown,
turn the drag other side up. Remove the upper cover board and
place the upper half of the flask, or “cope,” in position, as
shown at E.

In order to prevent the two layers of sand sticking together, the
surface of the sand at E should be covered with coal-dust. This
is done by shaking the coal-dust bag over the flask, after which
the dust on the pattern may be removed by blowing. The cope is
then filled with sand and rammed in exactly the same manner as in
the case of the drag.

After the ramming is done a number of vent holes are made, as
shown at F, from the surface of the mold to the pattern, in order
to allow the escape of air and steam when the mold is being
poured. These vent holes may be made by pushing a wire about the
size of a knitting-needle down through the sand until it touches
the pattern. The “sprue,” or pouring-hole, is next cut, by means
of the sprue-cutter shown at the right, which consists of a piece
of thin brass or steel tubing about 3/4 in. in diameter.

Now comes the critical part of the molding operation—that of
lifting the cope from the drag. It is here that the amateur often
becomes discouraged, as the sand is liable to fall out of the
cope and spoil the mold; but with a little practice and patience
the molder can lift the cope every time without breaking it, as
shown at G.

The next operation is that of cutting the gate, which carries the
molten metal from the sprue to the opening left by the pattern.
This is done with a spoon, a channel being cut about 3/4 in. wide
and about 1/4 in. deep. The pattern is then drawn from the mold,
as shown at H, by driving a sharp pointed steel rod into the
pattern and lifting it from the sand. When a metal pattern is
used a thread rod is used, which is screwed into a tapped hole in
the pattern. Before drawing it is well to tap the drawing-rod
lightly with another and larger rod, striking it in all
directions and thus loosening the sand slightly from the pattern.
Some molders tap the pattern gently when withdrawing, as shown at
H, in order to loosen any sand which has a tendency to stick.

After drawing the pattern, place the cope back on the drag, as
shown at J. Place a brick or other flat, heavy object on top of
the mold above the pattern, to prevent the pressure of the melted
metal separating the two halves of the mold, and then pour.

III—Melting and Pouring

Having prepared one or more molds, the next operation is that of
melting and pouring. An ordinary cast-iron glue-pot makes a good
crucible and can be easily handled by a pair of tongs, made out
of steel rod, as shown in the sketch. In order to hold the tongs
together a small link can be slipped on over the handle, thus
holding the crucible securely.

A second piece of steel rod bent in the form of a hook at the end
is very useful for supporting the weight of the crucible and
prevents spilling the molten metal should the tongs slip off the
crucible. The hook is also useful for removing the crucible from
the fire, which should be done soon after the metal is entirely
melted, in order to prevent overheating. The metal should be
poured into the mold in a small stream, to give the air a chance
to escape, and should not be poured directly into the center of
the opening, as the metal will then strike the bottom hard enough
to loosen the sand, thus making a dirty casting.

Fig. 4—Pouring the Metal

If, after being poured, the mold sputters and emits large volumes
of steam, it shows that the sand is too wet, and the castings in
such cases will probably be imperfect and full of holes.

A mold made in the manner previously described may be poured with
any desired metal, but a metal which is easily melted will give
the least trouble. One of the easiest metals to melt and one
which makes very attractive castings is pure tin. Tin melts at a
temperature slightly above the melting point of solder, and,
although somewhat expensive, the permanent brightness and
silver-like appearance of the castings is very desirable. A good
“white metal” may be made by mixing 75% tin, 15%
lead, 5% zinc
and 5% antimony. The object of adding antimony to an alloy is to
prevent shrinkage when cooling.

A very economical alloy is made by melting up all the old
type-metal, babbitt, battery zincs, white metal and other scrap
available, and adding a little antimony if the metal shrinks too
much in cooling. If a good furnace is available, aluminum can be
melted without any difficulty, although this metal melts at a
higher temperature than any of the metals previously mentioned.

In casting zincs for batteries a separate crucible, used only for
zinc, is very desirable, as the presence of a very small amount
of lead or other impurity
will cause the batteries to polarize. A
very good way to make the binding posts is to remove the binding
posts from worn-out dry batteries and place them in the molds in
such a way that the melted zinc will flow around them.

The time required for a casting to solidify varies with the size
and shape of the casting, but unless the pattern is a very large
one about five minutes will be ample time for it to set. The
casting is then dumped out of the mold and the sand brushed off.
The gate can be removed with either a cold chisel or a hacksaw,
and the casting is then ready for finishing.

Battery Switch

In cases where batteries are used in series and it is desirable
to change the strength and direction of the current frequently,
the following device will be found most convenient. In my own
case I used four batteries, but any reasonable number may be
used. Referring to the figure, it will be seen that by moving
the switch A toward the left the current can be reduced from four
batteries to none, and then by moving the switch B toward the
right the current can be turned on in the opposite direction to
the desired strength. In the various positions of these two
switches the current from each individual cell, or from any
adjacent pair of cells, may be used in either
direction.

Contributed by Harold S. Morton, Minneapolis.

An Optical Illusion

An Optical Illusion

The engraving shows a perfectly straight boxwood rule laid over a
number of turned brass rings of various sizes. Although the
effect in the illustration is less pronounced than it was in
reality, it will be noticed that the rule appears to be bent, but
sighting along the rule from one end will show that it is
perfectly straight.

The brass rings also appear distorted. The portions on one side
of the rule do not appear to be a continuation of those on the
other, but that they really are can be proved by sighting in the
same manner as before.

Contributed by Draughtsman, Chicago.

New Method of Lifting a Table

To perform this feat effectively the little device illustrated
will be required. To make it take a sheet-iron band, A, 3/4 in.
wide and attach a strap to fasten on the forearm between the
wrist and elbow. Put a sharp needle point, B, through the
sheet-iron so that it extends 3/4 in. outward. Make one of these
pieces for each arm.

In lifting the table first show the hands unprepared to the
audience and also a tight table, removing the cover to show that
the surface of the table is not prepared in any way. Then replace
the table, rest the hands upon it and at the same time press the
needle points in the arm pieces into the wood of the table, which
will be sufficient to hold it, says a correspondent of the
Sphinx. Then walk down among the audience.

How to Make a Paddle Boat

Paddle Boat in Operation

Detail of Paddle Boat

A rowboat has several disadvantages. The operation of the oars is
both tiresome and uninteresting, and the oarsman is obliged to
travel, backward. By replacing the oars with paddles, as shown in
the illustration, the operator can see where he is going and
enjoy the exercise much better than with oars. He can easily
steer the boat with his feet, by means of a pivoted stick in the
bottom of the boat, connected by cords to the rudder. At the
blacksmith shop have a 5/8-in. shaft made, as shown at A, Fig. 2.
It will be necessary to furnish a sketch giving all the
dimensions of the shaft, which should be designed to suit the
dimensions of the boat, taking care that sufficient clearance is
allowed, so that the cranks in revolving will not strike the
operator’s knees. If desired, split-wood handles may be placed on
the cranks, to prevent them from rubbing the hands.

The bearings, B, may be made of hardwood, but preferably of iron
pipe filled with melted babbitt. If babbitt is used, either
thoroughly smoke or chalk the shaft or wrap paper around it to
prevent the babbitt sticking. The pieces of pipe may be then
fastened to the boat by means of small pipe straps, such as may
be obtained at any plumber’s at a very small cost.

The hubs, C, should be made of wood, drilled to fit the shaft and
mortised out to hold the paddles, D. The covers, E, may be
constructed of thin wood or galvanized iron and should be braced
by triangular boards, as shown in Fig. 1. If galvanized iron is
used, it should be exposed to the weather two or three months
before painting, or the paint will come off, spoiling its
appearance.

Peculiar Properties of Ice

Experiment with a Block of Ice

Of all the boys who make snowballs probably few know what occurs
during the process. Under ordinary conditions water turns to ice
when the temperature falls to 32°, but when in motion, or under
pressure, much lower temperatures are required to make it a
solid. In the same way, ice which is somewhat below the freezing
point can be made liquid by applying pressure, and will remain
liquid until the pressure is removed, when it will again return
to its original state. Snow, being simply finely divided ice,
becomes liquid in places when compressed by the hands, and when
the pressure is removed the liquid portions solidify and unite
all the particles in one mass. In extremely cold weather it is
almost impossible to make a snowball, because a greater amount of
pressure is then required to make the snow liquid.

This process of melting and freezing under different pressures
and a constant temperature is well illustrated by the experiment
shown in Figs. 1, 2 and 3. A block of ice, A, Fig. 1, is
supported at each end by boxes BB, and a weight, W, is hung on a
wire loop which passes around the ice as shown. The pressure of
the wire will then melt the ice and allow the wire to sink down
through the ice as shown in Fig. 2. The wire will continue to cut
its way through the ice until it passes all the way through the
piece, as shown in Fig. 3. This experiment not only illustrates
how ice melts under pressure, but also how it solidifies when the
pressure is removed, for the block will still be left in one
piece after the wire has passed through.

Another peculiar property of ice is its
tendency to flow. It may seem strange that ice should flow like
water, but the glaciers of Switzerland and other countries are
literally rivers of ice. The snow which accumulates on the
mountains in vast quantities is turned to ice as a result of the
enormous pressure caused by its own weight, and flows through the
natural channels it has made in the rock until it reaches the
valley below. In flowing through these channels it frequently
passes around bends, and when two branches come together the
bodies of ice unite the same as water would under the same
conditions. The rate of flow is often very slow; sometimes only
one or two feet a day, but, no matter how slow the motion may be,
the large body of ice has to bend in moving.

This property of ice is hard to illustrate with the substance
itself, but may be clearly shown by sealing-wax, which resembles
ice in this respect. Any attempt to bend a piece of cold
sealing-wax with the hands results in breaking it, but by placing
it between books, as shown on page 65, or supporting it in some
similar way, it will gradually change from the original shape
A, and assume the shape shown at B.

Return-Call Bell With One Wire

Wiring Diagram

To use only one wire for a return call bell connect up as shown
in the diagram, using a closed circuit or gravity battery, B. The
current is flowing through both bells all the time, the same as
the coils of a telegraph sounder, but is not strong enough to
ring both connected in series. Pressing either push button, P,
makes a short circuit of that bell and rings the one at the other
end of the line.

Contributed by Gordon T. Lane, Crafton, Pa.

Circuit Breaker for Induction Coils

Interrupter for Induction Coil

Amateurs building induction coils are generally bothered by the
vibrator contacts blackening, thus giving a high resistance
contact, whenever there is any connection made at all. This
trouble may be done away with by departing from the old single-contact
vibrator and using one with self-cleaning contacts as
shown. An old bell magnet is rewound full of No. 26 double
cotton-covered wire and is mounted upon one end of a piece of
thin sheet iron 1 in. by 5 in. as per sketch. To the other end of
the strip of iron is soldered a piece of brass 1/64 in. by 1/4
in. by 2 in., on each end of which has been soldered a patch of
platinum foil 1/4 in. square.

The whole is connected up and mounted on a baseboard as per
sketch, the contact posts being of 1/16 in. by 1/2 in. brass, bent
into shape and provided with platinum tipped thumb screws. The
advantage of this style of an interrupter is that at each stroke
there is a wiping effect at the heavy current contact which
automatically cleans off any carbon deposit.

In the wiring diagram, A is the circuit breaker; B, the induction
coil, and C, the battery.

Contributed by A. G. Ward, Wilkinsburg, Pa.

Spit Turned by Water Power

For a Summer Camp

Many of the Bulgarian peasants do their cooking in the open air
over bonfires. The illustration shows a laborsaving machine in
use which enables the cook to go away and leave meat roasting for
an hour at a time. The illustration shows how the spit to which
the meat is fastened is constantly turned by means of a slowly
moving water wheel. Some of our readers may wish to try the
scheme when camping out. The success depends upon a slow current,
for a fast-turning wheel will burn the meat.

A Short-Distance Wireless Telegraph

Wiring Diagram for Wireless Telegraph

The accompanying diagrams show a wireless-telegraph system that I
have used successfully for signaling a distance of 3,000 ft. The
transmitter consists of an induction coil, about the size used
for automobiles, a key or push-button for completing the circuit,
and five dry batteries. The small single-point switch is left
open as shown when sending a message, but when receiving it
should be closed in order that the electric waves from the
antenna may pass through the coherer. The coherer in this case is
simply two electric-light carbons sharpened to a wedge at one end
with a needle connecting the two, as shown. An ordinary telephone
receiver is connected in series with the coherer, as shown. To
receive messages hold the receiver to the ear and close the
switch, and answer by opening the switch and operating the key.

Contributed by Coulson Glick, Indianapolis.

Automatic Draft-Opener

Draft Regulator

A simple apparatus that will open the draft of the furnace at any
hour desired is illustrated. The parts are: A, furnace; B,
draft; C, draft chain; D, pulleys; E, wooden supports; F,
vertical lever; G, horizontal lever; H, cord; I, alarm clock; J,
weight. K shows where and how the draft is regulated during the
day, the automatic device being used to open it early in the
morning. The spool on the alarm clock is fastened to the alarm
key by sawing a slit across the top of the spool and gluing it
on. When the alarm goes off a cord is wound up on the spool and
pulls the horizontal lever up, which releases the vertical lever
and allows the weight to pull the draft open.

Contributed by Gordon Davis, Kalamazoo, Mich.

A Window Conservatory

Artistic Window Boxes

During the winter months, where house plants are kept in the
home, it is always a question how to arrange them so they can get
the necessary light without occupying too much room.

The sketch shows how a neat window conservatory may be made at
small cost that can be fastened on the house just covering a
window, which will provide a fine place for the plants. The frame
(Fig. 2) is made of about 2 by 2-in. material framed together as
shown in Fig. 3. This frame should be made with the three
openings of such a size that a four-paned sash, such as used for
a storm window, will fit nicely in them. If the four vertical
pieces that are shown in Fig. 2 are dressed to the right angle,
then it will be easy to put on the finishing corner boards that
hold the sash.

The top, as well as the bottom, is constructed with two small
pieces like the rafters, on which is nailed the sheathing boards
and then the shingles on top and the finishing boards on the
bottom.

How to Make an Electroscope

Simple Electroscope

An electroscope for detecting electrified bodies may be made out
of a piece of note paper, a cork and a needle. Push the needle
into the cork, and cut the paper in the shape of a small arrow.
Balance the arrow on the needle as shown in the sketch, and the
instrument will then be complete. If a piece of paper is then
heated over a lamp or stove and rubbed with a piece of cloth or a
small broom, the arrow will turn when the paper is brought near
it.

Contributed by Wm. W. Grant, Halifax, N. S., Canada.

Miniature Electric Lighting

Fig. 1

Fig. 2

Producing electric light by means of small bulbs that give from
one-half to six candle power, and a suitable source of power, is
something that will interest the average American boy.

These circular bulbs range from 1/4 to 2 in. in diameter, and
cost 27 cents each complete with base. They are commonly known as
miniature battery bulbs, since a battery is the most popular
source of power. The 1/2-cp. bulbs are usually 2-1/2 volts and
take 1/4 ampere of current. It requires about three medium dry
cells to operate it. However, there is now upon the market a
battery consisting of 3 small dry cells connected in series, put
up in a neat case with 2 binding posts, which sells for 25 cents.
This is more economical than dry cells, as it gives about 4 volts
and 3 amperes. It will run as large a lamp a 3-1/2 volts, 1 cp.,
for some time very satisfactorily. More than one lamp can be run
by connecting the bulbs in parallel, as indicated by Fig. 1,
which shows the special battery with 3 dry cells in the case, and
the 2 binding posts for connection with the bulbs. In this case
it is also advisable to connect several batteries in parallel
also, so as to increase the current, but maintain the voltage
constant. Thus the individual cells are in multiple series, i.
e., multiples of series of three. By keeping in mind the ampere
output of the battery and rating of the lamp, one can regulate
the batteries as required. It must be remembered, in this
connection, that any battery which is drawn upon for half of its
output will last approximately three times as long, as if drawn
upon for its total output. Thus, in any system of lamps, it is
economical to provide twice as many batteries as necessary. This
also supplies a means of still maintaining the candle power when
the batteries are partially exhausted, by connecting them in
series. However, this must be done with very great caution, as
the lights will be burnt out if the voltage is too high.

Persons living in the city will find an economical means of
lighting lamps by securing exhausted batteries from any garage,
where they are glad to have them taken away. A certain number of
these, after a rest, can be connected up in series, and will give
the proper voltage.

In conclusion, for battery power: Connecting batteries in series
increases the voltage, and slightly cuts down the current or
amperage, which is the same as that of one battery; while
connecting batteries in parallel increases the amperage, but
holds the voltage the same as that of one cell. Thus, if the
voltage and amperage of any cell be known, by the proper
combination of these, we can secure the required voltage and
amperage to light any miniature lamp. And it might be said that
dry cells are the best for this purpose, especially those of low
internal resistance.

For those having a good water supply there is a more economical
means of maintenance, although the first cost is greater. Fig. 2
shows the scheme. A small dynamo driven by a water motor attached
to a faucet, generates the power for the lights. The cost of the
smallest outfit of the kind is about $3 for the water motor and
$4 for the dynamo. This dynamo has an output of 12 watts, and
will produce from 18 to 25 cp., according to the water pressure
obtainable. It is advisable to install the outfit in the
basement, where the water pressure is the greatest, and then lead
No. 18 B & S. double insulated wire wherever needed. The dynamo
can also be used as a motor, and is wound for any voltage up to
ten. The winding should correspond to the voltage of the lamps
which you desire to run. However, if wound for 6 volts, one could
run parallel series of two 3-volt, 1-cp. lamps; making, as in
Fig. 3, 11 series, or 22 lights. If wound for 10 volts, it would
give 1-1/4 amperes and run four 6-cp. lamps. Thus, it will be
seen that any candle power lamp can be operated by putting the
proper number of lights in each series, and running the series in
parallel. So, to secure light by this method, we simply turn on
the water, and the water consumption is not so great as might be
imagined.

Fig. 3

For the party who has electric light in his house there is still
an easier solution for the problem of power. If the lighting
circuit gives 110 volts he can connect eleven 10-volt lamps in
series. These will give 3 cp. each, and the whole set of 11 will
take one ampere of current, and cost about the same as a 32-cp.
lamp, or 1-1/4 cents per hour. Simply connect the miniature
circuit to an Edison plug, and insert in the nearest lamp socket.
Any number of different candle power lamps can be used providing
each lamp takes the same amount of current, and the sum of their
voltages equals the voltage of the circuit used. This arrangement
of small lights is used to produce a widely distributed, and
diffused light in a room, for display of show cases, and for
Christmas trees. Of all these sources of power the two last are
the most economical, and the latter of these two has in its favor
the small initial cost. These lamps are by no means playthings or
experiments, but are as serviceable and practical as the larger
lamps.

Contributed by Lindsay Eldridge, Chicago.

How to Make a New Language

Anyone possessing a phonograph can try a very interesting and
amusing experiment without going to any expense. Remove the belt
and replace with a longer one, which can be made of narrow braid
or a number of strands of yarn. The new belt should be long
enough to allow crossing it, thus reversing the machine. This
reverses every sound on the record and changes it to such an
extent that very few words can be recognized.

How to Make a Cup-and-Saucer Rack

The rack is made of any suitable kind of wood, and the sides, A,
are cut just alike, or from one pattern. The shelves are made in
various widths to fit the sides at the places where they are
wanted. The number of shelves can be varied and to suit the size
of the dishes. Cup hooks are placed on top and bottom shelves. It
is hung on the wall the same as a picture from the molding.

Contributed by F. B. Emig, Santa Clara, Cal.

Reversing a Small Motor

Reverse for a Small Motor

All that is necessary for reversing the motor is a pole-changing
switch. Connect the two middle posts of the switch with each
other and the two outside posts with each other. Then connect one
of the outside posts of the switch to one brush of the motor and
one middle post to the other brush.

Connect one bar of the switch to one end of the field coil and
the other bar to one pole of the battery, and connect the other
pole of the battery to the other field coil. To reverse the
motor, simply change the switch.

Referring to the illustration, the letters indicate as follows:
FF, field of motor; BB, brushes of motor; AA, bars of
pole-changing switch; DD, center points of switch; CC, outside
points of switch.

Contributed by Leonard E. Parker, Plymouth, Ind.

To Drive Away Dogs

Shocking-Machine

The dogs in my neighborhood used to come around picking up
scraps. After I connected up my induction coil, as shown in the
sketch, we were not bothered with them. A indicates the ground;
B, switch; and C, a bait of meat, or a tempting bone.

Contributed by Geo. W. Fry, 903 Vine St., San Jose, Cal.

An Automatic Lock

Automatic Electric Lock for Doors

The illustration shows an automatic lock operated by electricity,
one cell being sufficient. When the circuit is broken a weight,
A, attached to the end of the armature B, tends to push the other
end of the armature into the screw eye or hook C, which is in the
door, thus locking the door.

To unlock the door, merely push the button E, The magnet then
draws the armature out of the screw eye and the door is unlocked.
The dotted line at D shows the position of the armature when the
circuit is complete and the door unlocked. The weight must be in
proportion to the strength of the magnet. If it is not, the door
will not lock, or would remain locked. The button can be hidden,
as it is the key to the lock.

Contributed by Claude B. Melchior, Hutchinson, Minn.

Experiment with Two-Foot Rule and Hammer

An Experiment in Equilibrium

An example of unstable equilibrium is shown in the accompanying
sketch. All that is needed is a 2-foot rule, a hammer, a piece of
string, and a table or bench. The experiment works best with a
hammer having a light handle and a very heavy head. Tie the ends
of the string together, forming a loop, and pass this around the
hammer handle and rule. Then place the apparatus on the edge of
the table, where it will remain suspended as shown.

Contributed by Geo. P. Schmidt, Culebra, Porto Rico, W. I.

Simple Current Reverser

Details of Reverser

On a block of hardwood draw a square (Fig. 1) and drill a hole in
each corner of the square. Fill these holes with
mercury and
connect them to four binding posts (Fig. 1).

On another block of wood fasten two wires, as shown in Fig. 2, so
that their ends can be placed in the holes in the first block.
Then connect up with the motor and battery as in Fig. 3. When the
block is placed on with the big arrow A pointing in the direction
indicated in Fig. 3, the current flows with the small arrows. To
reverse turn through an angle of 90 degrees (Fig. 4).

Contributed by F. Crawford Curry, Brockville, Ontario, Canada.

Alarm Clock to Pull up Furnace Draft

Automatic Time Draft-Opener

A stout cord, A, is attached to the draft B of the furnace, run
through a pulley, C, in the ceiling and has a window weight, D,
attached at the other end. A small stick is put through a loop in
the cord at about the level of the table top on which the alarm
clock F stands. The other end of stick E is placed under the key
G of the alarm clock. When the alarm rings in the early morning,
the key turns, the stick falls away, releasing the weight, which
pulls the draft open.

Contributed by Edward Whitney, 18 Gorham St., Madison, Wis.

How to Transmit Phonograph Music to a Distance

The Long-Distance Phonograph

An interesting experiment, and one calculated to mystify anyone
not in the secret, is to transmit the music or speech from a
phonograph to another part of the house or even a greater
distance. For an outdoor summer party the music can be made to
come from a bush, or tree, or from a bed of flowers. The
apparatus is not difficult to construct.

The cut shows the arrangement. Procure a long-distance telephone
transmitter, D, including the mouthpiece, and fasten it to the
reproducer of the phonograph. Also a watch case receiver, R,
which fasten to the horn. These parts may be purchased from any
electrical-supply house. Connect two wires to the transmitter,
running one direct to the receiver, and the other to the battery,
thence to a switch, S, and then to the receiver. The more
batteries used the louder will be the sound produced by the horn,
but avoid using too much battery or the receiver is apt to heat.

Contributed by Wm. J. Farley, Jr., Camden, N. J.

How to Make a Telescope

Homemade Telescope

With a telescope like the one here described, made with his own
hands, a farmer boy not many years ago discovered a comet which
had escaped the watchful eyes of many astronomers. First, get two
pieces of plate glass, 6 in. square and 1 in. thick, and break
the corners off to make them round, grinding the rough edges on a
grindstone. Use a barrel to work on, and fasten one glass on the
top of it in the center by driving three small nails at the sides
to hold it in place. Fasten, with pitch, a round 4-in. block of
wood in the center on one side of the other glass to serve as a
handle.

Use wet grain emery for coarse grinding. Take a pinch and spread
it evenly on the glass which is on the barrel, then take the
glass with the handle and move it back and forth across the lower
glass, while walking around the barrel; also rotate the glass,
which is necessary to make it grind evenly. The upper glass or
speculum always becomes concave, and the under glass or tool
convex.

Work with straight strokes 5 or 6 in. in length; after working 5
hours hold the speculum in the sunshine and throw the rays of the
sun onto a paper; where the rays come to a point gives the focal
length. If the glass is not ground enough to bring the rays to a
point within 5 ft., the coarse grinding must be continued, unless
a longer focal length is wanted.

Have ready six large dishes, then take 2 lb. flour emery and mix
in 12 qt. of water; immediately turn the water into a clean dish
and let settle 30 seconds; then turn it into another dish and let
settle 2 minutes, then 8 minutes, 30 minutes and 90 minutes,
being careful not to turn off the coarser emery which has
settled. When dry, turn the emery from the 5 jars into 5 separate
bottles, and label. Then take a little of the coarsest powder,
wetting it to the consistency of cream, and spread on the glass,
work as before (using short straight strokes 1-1/2 or 2 in.)
until the holes in the glass left by the grain emery are ground
out; next use the finer grades until the pits left by each
coarser grade are ground out. When the two last grades are used
shorten the strokes to less than 2 in. When done the glass should
be semi-transparent, and is ready for polishing.

When polishing the speculum, paste a strip of paper 1-1/3 in.
wide around the convex glass or tool, melt 1 lb. of pitch and
turn on to it and press with the wet speculum. Mold the pitch
while hot into squares of 1 in., with 1/4-in. spaces, as in Fig.
1. Then warm and press again with the speculum, being careful to
have all the squares touch the speculum, or it will not polish
evenly. Trim the paper from the edge with a sharp knife, and
paint the squares separately with jeweler’s rouge, wet till soft
like paint. Use a binger to spread it on with. Work the speculum
over the tool the same as when grinding, using straight strokes 2
in. or less.

Detail of Telescope Construction

When the glass is polished enough to reflect some light, it
should be tested with the knife-edge test. In a dark room, set
the speculum against the wall, and a large lamp, L, Fig. 2, twice
the focal length away. Place a large sheet of pasteboard, A, Fig.
2, with a small needle hole opposite the blaze, by the side of
the lamp, so the light from the blaze will shine onto the glass.
Place the speculum S, Fig. 2, so the rays from the needle hole
will be thrown to the left side of the lamp (facing the
speculum), with the knife mounted in a block of wood and edgeways
to the lamp, as in K, Fig. 2. The knife should not be more than 6
in. from the lamp. Now move the knife across the rays from left
to right, and look at the speculum with the eye on the right side
of the blade. When the focus is found, if the speculum is ground
and polished evenly it will darken evenly over the surface as the
knife shuts off the light from the needle hole. If not, the
speculum will show some dark rings, or hills. If the glass seems
to have a deep hollow in the center, shorter strokes should be
used in polishing; if a hill in the center, longer strokes. The
polishing and testing done, the speculum is ready to be silvered.
Two glass or earthenware dishes, large enough to hold the
speculum and 2 in. deep, must be procured. With pitch, cement a
strip of board 8 in. long to the back of the speculum, and lay
the speculum face down in one of the dishes; fill the dish with
distilled water, and clean the face of the speculum with
nitric acid,
until the water will stick to it in an unbroken film.

The recipe for silvering the speculum is:

Mix solution D and make up to 25 fluid oz. with distilled water,
pour into a bottle and carefully put away in a safe place for
future use, as it works better when old:

Now take solution A and set aside in a small bottle one-tenth of
it, and pour the rest into the empty dish; add the ammonia
solution drop by drop; a dark brown precipitate will form and
subside; stop adding ammonia solution as soon as the bath clears.
Then add solution B, then ammonia until bath is clear. Now add
enough of the solution A, that was set aside, to bring the bath
to a warm saffron color without destroying its transparency. Then
add 1 oz. of solution D and stir until bath grows dark. Place the
speculum, face down, in the bath and leave until the silver
rises, then raise the speculum and rinse with distilled water.
The small flat mirror may be silvered the same way. When dry, the
silver film may be polished with a piece of chamois skin, touched
with rouge, the polishing being accomplished by means of a light
spiral stroke.

Fig. 3 shows the position of the glasses in the tube, also how
the rays R from a star are thrown to the eyepiece E in the side
of the tube. Make the tube I of sheet iron, cover with paper and
cloth, then paint to make a non-conductor of heat or cold. Make
the mounting of good seasoned lumber.

Thus an excellent 6-in. telescope can be made at home, with an
outlay of only a few dollars. My telescope is 64 in. long and
cost me just $15, but I used all my spare time in one winter in
making it. I first began studying the heavens through a spyglass,
but an instrument such as I desired would cost $200—more than I
could afford. Then I made the one described, with which I
discovered a new comet not before observed by
astronomers.

John E. Mellish.

How to Make “Freak” Photographs

Arrangement of Prisms

The “freak” pictures of well-known people which were used by some
daily newspapers recently made everybody wonder how the distorted
photographs were made. A writer in Camera Craft gives the secret,
which proves to be easy of execution. The distortion is
accomplished by the use of prisms, as follows: Secure from an
optician or leaded-glass establishment, two glass prisms,
slightly wider than the lens mount. The flatter they are the less
they will distort. About 20. deg. is a satisfactory angle. Secure
them as shown by the sectional sketch, using strawboard and black
paper. Then make a ring to fit over the lens mount and connect it
with the prisms in such a way as to exclude all light from the
camera except that which passes through the face of the prisms.
The inner surface of this hood must be dull black. The paper
which comes around plates answers nicely. If the ring which slips
over the lens mount is lined with black velvet, it will exclude
all light and hold firmly to the mount, Place over lens, stop
down well after focusing, and proceed as for any picture.

Another Electric Lock

Simple Electric Lock

The details of the construction of an electrically operated lock
are shown in the illustration. When the door is closed and the
bolt A pushed into position, it automatically locks. To unlock,
push the button D, which act will cause the electromagnet to
raise the latch C, when the bolt may be drawn and the door
opened.

Contributed by A. D. Zimmerman, Boody, Ill.

How to Mix Plaster of Paris

For the mixing of plaster of Paris for any purpose, add the
plaster gradually to the water, instead of the contrary, says the
Master Painter. Do not stir it, just sprinkle it in until you
have a creamy mass without lumps. Equal parts of plaster and
water is approximately the correct proportion. The addition of a
little vinegar or glue water will retard the setting of the
plaster, but will not preserve its hardening. Marshmallow powder
also retards the setting. In this way the plaster may be handled
a long time without getting hard. If you wish the plaster to set
extra hard, then add a little sulphate of potash, or powdered
alum.

Enlarging with a Hand Camera

Making Large Pictures with a Small Camera

Everyone who owns a hand camera has some pictures he would like
enlarged. It is not necessary to have a large camera to do this,
as the process is exceedingly simple to make large pictures from
small negatives with the same hand camera.

A room from which all light may be excluded and a window through
which the light can enter without obstruction from trees or
nearby buildings, with a shelf to hold the camera and a table
with an upright drawing-board attached, complete the arrangement.
The back is taken out of the camera and fitted close against the
back of the shelf, which must be provided with a hole the same
size and shape as the opening in the back of the camera. The
negative used to make the enlarged print is placed in the shelf
at A, Fig. 1. The rays of the clear, unobstructed light strike
the mirror, B, and reflect through the negative, A, through the
lens of the camera and on the board, as shown in Fig. 2. The
window must be darkened all around the shelf.

After placing the negative and focusing the lens for a clear
image on the board, the shutter is set and a bromide paper is
placed on the board. The paper is exposed, developed and fixed by
the directions that are enclosed in the package of bromide
papers.

Positioning A Hanging Lamp

Don’t pull a lamp hung by flexible cord to one side with a wire
and then fasten to a gas pipe. I have seen a wire become red hot
in this manner. If the lamp hung by a cord must be pulled over,
use a string.

A Curious Compressed Air Phenomenon

Experiment with Spool and Card

Push a pin through an ordinary business card and place the card
against one end of a spool with the pin inside the bore, as shown
in the sketch. Then blow through the spool, and it will be found
that the card will not be blown away, but will remain suspended
without any visible support. This phenomenon is explained by the
fact that the air radiates from the center at a velocity which is
nearly constant, thereby producing a partial vacuum between the
spool and the card. Can the reader devise a practical application
of this contrivance?

Simple Switch for Reversing a Current

Simple Current-Reversing Switch

Take two strips of copper or brass and fasten them together by
means of gutta-percha (Fig. 1); also provide them with a handle.
Saw out a rectangular block about one and one-half times as long
as the brass strips and fasten to it at each end two forked
pieces of copper or brass, as in Fig. 2. Fasten on the switch
lever, as at A and B, Fig. 2, so that it can rotate about these
points. Connect the wires as shown in Fig. 3. To reverse, throw
the lever from one end of the block to the other.

Contributed by R. L. Thomas, San Marcos, Tex.

Novel Mousetrap

A Baitless Trap

A piece of an old bicycle tire and a glass fruit jar are the only
materials required for making this trap. Push one end of the tire
into the hole, making sure that there is a space left at the end
so that the mice can get in. Then bend the other end down into a
fruit jar or other glass jar. Bait may be placed in the jar if
desired, although this is not necessary.

Contributed by Geo. G. McVicker, North Bend, Neb.

Polishing Nickel

A brilliant polish may be given to tarnished nickel by immersing
in alcohol and 2 per cent of
sulphuric acid from 5 to 15 seconds.
Take out, wash in running water, rinse in alcohol, and rub dry
with linen cloth.

Homemade Arc Light

Arc Light

By rewinding an electric-bell magnet with No. 16 wire and
connecting it in series with two electric-light carbons, as shown
in the sketch, a small arc will be formed between the carbon
points when the current is applied. In the sketch, A is the
electric-bell magnet; B, the armature; C C, carbon sockets; D,
carbons, and E E, binding posts. When connected with 10 or 12 dry
batteries this lamp gives a fairly good light.

Contributed by Morris L. Levy, San Antonio, Tex.

Lighting an Incandescent Lamp with an Induction Coil

Geissler Tube

An incandescent lamp of low candlepower may be illuminated by
connecting to an induction coil in the manner shown in the
sketch. One wire is connected to the metal cap of the lamp and
the other wire is fastened to the glass tip. If the apparatus is
then placed in the dark and the current turned on, a peculiar
phosphorescent glow will fill the whole interior of the lamp. The
induction coil used for this purpose should give a spark about
1/2 in. long or more.

Contributed by Joseph B. Bell, Brooklyn.

How to Make a Jump-Spark Coil

Jump-Spark Coil

The induction coil is probably the most popular piece of
apparatus in the electrical laboratory, and particularly is it
popular because of its use in experimental wireless telegraphy.
Ten years ago wireless telegraphy was a dream of scientists;
today it is the plaything of school-boys and thousands of
grown-up boys as well.

Divested of nearly all technical phrases, an induction coil may
be briefly described as a step-up transformer of small capacity.
It comprises a core consisting of a cylindrical bundle of
soft-iron wires cut to proper length. By means of two or more
layers of No. 14 or No. 16 magnet wire, wound evenly about this
core, the bundle becomes magnetized when the wire terminals are
connected to a source of electricity.

Should we now slip over this electromagnet a paper tube upon
which has been wound with regularity a great and continuous
length of No. 36 magnet wire, it will be found that the lines of
force emanating from the energized core penetrate the new
coil-winding almost as though it were but a part of the surrounding
air itself, and when the battery current is broken rapidly a
second electrical current is said to be induced into the second
coil or secondary.

All or any of the parts of an induction coil may be purchased
ready-made, and the first thing to do is to decide which of the
parts the amateur mechanic can make and which would be better to
buy ready-made. If the builder has had no experience in
coil-winding it would probably pay to purchase the secondary coil
ready-wound, as the operation of winding a mile or more of fine
wire is very difficult and tedious, and the results are often
unsatisfactory. In ordering the secondary it is always necessary
to specify the length of spark desired.

The following method of completing a 1-in. coil illustrates the
general details of the work. The same methods and circuits apply
to small and larger coils. The ready-made secondary is in solid
cylindrical form, about 6 in. long and 2-5/8 in. diameter, with a
hole through the winding 1-1/4 in. in diameter, as shown in Fig.
1. The secondary will stand considerable handling without fear of
injury, and need not be set into a case until the primary is
completed. The primary is made of fine annealed No. 24 iron wire
cut 7 in. or 8 in. in length, as the maker prefers, and bundled
to a diameter of 7/8 in. The wires may be straightened by rolling
two or three at a time between two pieces of hard wood. If the
amateur has difficulty in procuring this wire, the entire core
may be purchased ready-made.

After the core wires are bundled, the core is wrapped with one or
two layers of manila paper. The straighter the wire the more iron
will enter into the construction of the core, which is desirable.
Beginning half an inch from one end, No. 16 cotton-covered
magnet wire is wound from one end to the other evenly and then
returned, making two layers, and the terminals tied down to the
core with twine. Core and primary are then immersed in boiling
paraffine wax to which a small quantity of resin and beeswax has
been added. This same wax may be used later in sealing the
completed coil into a box. Over this primary is now wrapped one
layer of okonite tape, or same thickness of heavily shellacked
muslin. This completed primary will now allow of slipping into
the hole in the secondary.

Should the secondary have been purchased without a case, a wooden
box of mahogany or oak is made, large enough to contain the
secondary and with an inch to spare all around, with room also
for a small condenser; but if it is not convenient to do this
work, a box like that shown in Fig. 2 may be purchased at a small
cost. A 7/8-in. hole is bored in the center of one end, through
which the primary core projects 1/8 in. This core is to be used
to attract magnetically the iron head of a vibrating interrupter,
which is an important factor of the coil. This interrupter is
shaped as in Fig. 4, and is fastened to the box in such a way
that the vibrator hammer plays in front of the core and also that
soldered connections may be made inside the box with the screws
used in affixing the vibrator parts to the box. The condenser is
made of four strips of thin paper, 2 yd. long and 5 in. wide, and
a sufficient quantity of tinfoil. When cut and laid in one
continuous length, each piece of tin-foil must overlap the
adjoining piece a half inch, so as to form a continuous
electrical circuit. In shaping the condenser, one piece of the
paper is laid down, then the strip of tin-foil, then two strips
of paper and another layer of foil, and finally the fourth strip
of paper. This makes a condenser which may be folded, beginning
at one end and bending about 6 in. at a time. The condenser is
next wrapped securely with bands of paper or tape, and boiled in
pure paraffine wax for one hour, after which it is pressed under
considerable weight until firm and hard. One of the sheets of
tin-foil is to form one pole of the condenser, and the other
sheet, which is insulated from the first, forms the other pole or
terminal. (This condenser material is purchasable in long strips,
ready for assembling.)

The wiring diagram, Fig. 3, shows how the connections are made.
This method of connecting is suitable for all coils up to 1-1/2
in. spark, but for larger coil better results will be obtained by
using an independent type of interrupter, in which a separate
magnet is used to interrupt the circuit. Besides the magnetic
vibrators there are several other types,
such as the mercury
dash-pot and rotary-commutator types, but these will become
better known to the amateur as he proceeds in his work and
becomes more experienced in coil operation.

Combined Door Bell and Electric Alarm

This device consists of a battery and bell connection to an alarm
clock which also acts as a door bell, the whole being mounted on
a board 18 in. long and 12 in. wide.

Referring to the sketch accompanying this article, the letters
indicate as follows: A, bell; B, battery ; C, switch; D, V-shaped
copper strip; E, copper lever with 1-in. flange turned on one
side, whole length, 4 in.; F, spring to throw lever E down in
V-shaped piece to make connection; G, lever to hold out E when
device is used as a door bell; lines H, go, one from bell, A, and
one from battery, B, to the door; I, shelf for clock.

See that the ring in the alarm key of the clock works easily, so
that when it is square across the clock it will drop down. Fasten
a piece of copper about 1 in. long to key, then wind the alarm
just enough so that the key stands straight up and down. Place
the clock on the shelf and the key under the flange of lever E.
Pull lever G down out of the way and close the lever on the
switch. The alarm key will turn and drop down, letting lever E
drop into the V-shaped piece D and make connection.

For the door-bell connection close lever on switch C, and put G
up so that D and E do not come in contact. If anyone is ill and
you do not want the bell to ring, open switch C.

The wiring for this device may all be on the back of the board.
The switch and levers are fastened with small screw bolts, which
allows wiring at the back. Saw two spools in half and fasten the
halves to the four corners of the board at the back, and the
apparatus may be put up where one likes.

To Build a Small Brass Furnace

Bend a piece of stout sheet iron 23 in. by 12 in. round so that
the inside diameter is 7 in., and then rivet the seam. Fit in a
round piece of sheet iron for the bottom. Make a hole about the
size of a shilling in the side, 2 in. from the bottom. This is
for blowing.

Line the furnace, bottom and sides with fire-clay to a depth of
1/2 in. Use charcoal to burn and an ordinary bellows for blowing,
says the Model Engineer, London. The best blast is obtained by
holding the nozzle of the bellows about an inch from the hole,
instead of close to it.

Avoid Paper Lamp Shades

Don’t wrap paper around a lamp for a shade. You might go away and
forget it and a fire might be started from the heat. Use a glass
or metal shade. That is what they are for.

Why Gravity Batteries Fail to Work

Setting Up a Gravity Battery

Many amateur electricians and some professionals have had
considerable trouble with gravity batteries. They follow
directions carefully and then fail to get good results. The usual
trouble is not with the battery itself, but with the circuit. A
gravity battery is suitable only for a circuit which is normally
closed. It is therefore undesirable for electric bells, induction
coils and all other open-circuit apparatus. The circuit should
also have a high resistance. This makes it impractical for
running fan motors, as the motor would have to be wound with fine
wire and it would then require a large number of batteries to
give a sufficiently high voltage.

To set up a gravity battery: Use about 3-1/2 lb. of blue stone,
or enough to cover the copper element 1 in. Pour in water
sufficient to cover the zinc 1/2 in. Short-circuit for three
hours, and the battery is ready for use. If desired for use
immediately, do not short-circuit, but add 5 or 6 oz. of zinc
sulphate.

Keep the dividing line between the blue and white liquids about
1/2 in. below the bottom of the zinc. If too low, siphon off some
of the white liquid and add the same amount of water, but do not
agitate or mix the two solutions. This type of battery will give
about 0.9 of a volt, and should be used on a circuit of about 100
milli-amperes.

A Skidoo-Skidee Trick

How to Cut the Notches

In a recent issue of Popular Mechanics an article on “The Turning
Card Puzzle” was described and illustrated. Outside of the
scientific side involved, herein I describe a much better trick.
About the time when the expression “skidoo” first began to be
used I Invented the following trick and called it “Skidoo” and
“Skidee,” which created much merriment. Unless the trick is
thoroughly understood, for some it will turn one way, for others
the opposite way, while for others it will not revolve at all.
One person whom I now recall became red in the face by shouting
skidoo and skidee at it, but the thing would not move at all, and
he finally from vexation threw the trick into the fire and a new
one had to be made. Very few can make it turn both ways at will,
and therein is the trick.

Take a piece of hardwood 3/8 in. square and about 9 in. long. On
one of the edges cut a series of notches as indicated in Fig. 1.
Then slightly taper the end marked B until it is nicely rounded
as shown in Fig. 2. Next make an arm of a two-arm windmill such
as boys make. Make a hole through the center of this one arm.
Enlarge the hole slightly, enough to allow a common pin to hold
the arm to the end B and not interfere with the revolving arm.
Two or three of these arms may have to be made before one is
secured that is of the exact proportions to catch the vibrations
right.

To operate the trick, grip the stick firmly in one hand, and with
the forward and backward motion of the other allow the first
finger to slide along the top edge, the second finger along the
side, and the thumb nail will then vibrate along the notches,
thus making the arm revolve in one direction. To make the arm
revolve in the opposite dlrection—keep the hand moving all the
time, so the observer will not detect the change which the hand
makes—allow the first finger to slide along the top, as in the
other movement, the thumb and second finger changing places: e.g.,
In the first movement you scratch the notches with the thumb
nail while the hand is going from the body, and in the second
movement you scratch the notches with the nail of the second
finger when the hand is coming toward the body, thus producing
two different vibrations. In order to make it work perfectly (?)
you must or course say “skidoo” when you begin the first
movement, and then, no matter how fast the little arm is
revolving when changed to the second movement you must say
“skidee” and the arm will immediately stop and begin revolving in
the opposite direction. By using the magic words the little arm
will obey your commands instantly and your audience will be
mystified. If any of your audience presume to dispute, or think
they can do the same let them try it. You will no doubt be
accused of blowing or drawing in your breath, and many other
things in order to make the arm operate. At least it is amusing.
Try it and see.

Contributed by Charles Clement Bradley, Toledo, Ohio.

Effects of Radium

Radium acts upon the chemical constituents of glass, porcelain
and paper, imparting to them a violet tinge; changes white
phosphorus to yellow, oxygen to ozone, affects photograph plates
and produces many other curious chemical changes.

Naval Speed Record

On its official trial trip the British torpedo boat destroyer
“Mohawk” attained the record speed of a little over 39 miles an
hour.

How to Enlarge from Life in the Camera

Magnified Nine Diameters

Usually the amateur photographer gets to a point in his work
where the miscellaneous taking of everything in sight is somewhat
unsatisfying: There are many special fields he may enter, and one
of them is photomicrography. It is usually understood that this
branch of photography means an expensive apparatus. If the worker
is not after too high a magnification, however, there is a very
simple and effective means of making photomicrographs which
requires no additional apparatus that cannot be easily and
quickly constructed at home.

Reproduced with this article is a photograph of dandelion seeds—a
magnification of nine diameters or eighty-one times. The
apparatus which produced this photograph consisted of a camera of
fairly long draw, a means for holding it vertical, a short-focus
lens, and, if possible, but not essential, a means for focusing
that lens in a minute manner. On top of the tripod is the folding
arrangement, which is easily constructed at home with two hinged
boards, an old tripod screw, an old bed plate from a camera for
the screw to fit in, and two sliding brass pieces with sets crews
that may be purchased from any hardware store under the name of
desk sliding braces. To the front board is attached a box,
carrying the lens and the bed of the sliding object carrier,
which can be moved forward and back by the rack and pinion, that
also can be obtained from hardware stores. If the bed for the
object carrier be attached to the bed of the camera instead of to
the front board, the object carrier need have no independent
movement of its own, focusing being done by the front and back
focus of the camera; but this is less satisfactory, particularly
when accurate dimensions are to be determined, says the
Photographic Times. This outfit need not be confined to seeds
alone, but small flowers, earth, chemicals, insects, and the
thousand and one little things of daily life—all make beautiful
subjects for enlarged photographs. These cannot be made by taking
an ordinary photograph and enlarging through a lantern. When a
gelatine dry plate is magnified nine diameters, the grains of
silver in the negative will be magnified also and produce a
result that will not stand close examination. Photographs made by
photomicrography can be examined like any other photographs and
show no more texture than will any print.

Steel Pen Used in Draftsman’s Ink Bottle Cork

A steel pen makes an ideal substitute for a quill in the stopper
of the draftsman’s ink bottle. The advantage of this substitute
is that there is always one handy to replace a broken or lost
pen, while it is not so with the quill.

Contributed by George C. Madison, Boston, Mass.

How to Make a Pilot Balloon
By E. Goddard Jorgensen

Pattern for Cutting the Segments

Unusual interest is being displayed in ballooning, and as it is
fast becoming the favorite sport many persons would like to know
how to construct a miniature balloon for making experiments. The
following table will give the size, as well as the capacity and
lifting power of pilot balloons:

The material must be cut in suitable shaped gores or segments. In
this article we shall confine ourselves to a 10-ft. balloon. If
the balloon is 10 ft. in diameter, then the circumference will be
approximately 3-1/7 times the diameter, or 31 ft. 5 in. We now
take one-half this length to make the length of the gore, which
is 15 ft. 7-1/2 in. Get a piece of paper 15 ft. 7-1/2 in. long
and 3 ft. wide from which to cut a pattern, Fig. 1. A line, AB,
is drawn lengthwise and exactly in the middle of the paper, and a
line, CD, is drawn at right angles to AB and in the middle of the
paper lengthways. The intersecting point of AB and CD is used for
a center to ascribe a circle whose diameter is the same as the
width of the paper, or 3 ft. Divide one-quarter of the circle
into 10 equal parts and also divide one-half of the line AB in 10
equal parts. Perpendicular lines are drawn parallel with the line
CD intersecting the division points made on the one-half line
AB. Horizontal and parallel lines with AB are drawn intersecting
the division points made on the one-quarter circle and
intersecting the perpendicular line drawn parallel with CD. A
line is now drawn from B to E and from E to F, and so on, until
all the intersecting lines are touched and the point C is
reached. This will form the proper curve to cut the pattern. The
paper is now folded on the line AB and then on the line CD,
keeping the marked part on the outside. The pattern is now cut,
cutting all four quarters at the same time, on the curved line
from B to C. When the paper is unfolded you will have a pattern
as shown in Fig. 2. This pattern is used to mark the cloth, and
after marked is cut the same shape and size.

Sewing Segments Together

The cloth segments are sewed together, using a fine needle and
No. 70 thread, making a double seam as shown in Fig. 3. When all
seams are completed you will have a bag the shape shown in Fig.
4. A small portion of one end or a seam must be left open for
inflating. A small tube made from the cloth and sewed into one
end will make a better place for inflating and to tie up tightly.

It is now necessary to varnish the bag in order to make it retain
the gas. Procure 1 gal. of the very best heavy body, boiled
linseed oil and immerse the bag in it. The surplus oil is
squeezed out by running the bag through an ordinary clothes
wringer several times. The bag is now placed in the sun for a
thorough drying. Put the remaining oil in a kettle with 1/8 lb.
of beeswax and boil well together. This solution is afterward
diluted with turpentine so it will work well. When the bag is dry
apply this mixture by rubbing it on the bag with a piece of
flannel. Repeat this operation four times, being sure of a
thorough drying in the sun each time. For indoor coating and
drying use a small amount of
plumbic oxide. This will dry rapidly
in the shade and will not make the oil hard.

Fill the bag with air by using a pair of bellows and leave it
over night. This test will show if the bag is airtight. If it is
not tight then the bag needs another rubbing. The next operation
is to fill the bag with gas.

Fig. 5—The Hydrogen Generator

Hydrogen gas is made from iron and
sulphuric acid. The amounts
necessary for a 10-ft. balloon are 125 lb. of iron borings and
125 lb. of sulphuric acid.
1 lb. of iron, 1 lb. of sulphuric acid
and 4 lb. of water will make 4 cu. ft. of gas in one hour. Secure
two empty barrels of about 52 gal. capacity and connect them, as
shown in Fig. 5, with 3/4-in. pipe. In the barrel, A, place the
iron borings and fill one-half full of clear water. Fill the
other barrel, B, with water 2 in. above the level of the water in
barrel A. This is to give a water pressure head against foaming
when the generator is in action. About 15 lb. of lime should be
well mixed with the water in the barrel B. All joints must be
sealed with plaster of Paris. Pour in one-half of the acid into
the barrel, A, with the iron borings. The barrels are kept tight
while the generation is going on with the exception of the
outlet, C, to the bag. When the action is stopped in the
generator barrel, A, let the solution run out and fill again as
before with water and acid on the iron borings. The outlet, C,
should be always connected with the bag while the generator is in
action. The 3/4-in. pipe extending down into the cooling tank,
B, should not enter into the water over 8 in. When filled with
gas the balloon is ready for a flight at the will of the
operator.

How to Clean a Clock

It is very simple to clean a clock, which may sound rather
absurd. For an amateur it is not always necessary to take the
clock to pieces. With a little care and patience and using some
benzine, a clean white rag, a sable brush and some oil a clock
can be cleaned and put into first-class running order. The
benzine should be clean and free from oil. You can test benzine
by putting a little on the back of the hand; if it is good it
will dry off, leaving the hand quite clean, but if any grease
remains on the hand, it is not fit to use.

The oil should be of the very best that can be procured.
Vegetable oils should never be used. Clock oil can be procured
from your druggist or jeweler. All loose dirt should be removed
from the works by blowing with bellows, or a fan, or dusting with
a dry brush; in the latter case great care should be exercised
not to injure any of the parts. Dip the brush in the benzine and
clean the spindles and spindle holes, and the teeth of the
escapement wheel. After washing a part, wipe the brush on the rag
and rinse in the benzine; this should be repeated frequently,
until no more dirt is seen.

When the clock has dried, oil the spindle holes carefully; this
may be done with a toothpick or a sliver of woodcut to a fine
point. Oil the tooth of the escapement wheel slightly, using a
fine brush.

How to Make Blueprint Lantern Slides

Lantern slides of a blue tone that is a pleasing variety from the
usual black may be made from spoiled or old plates which have not
been developed, by fixing, washing well and then dipping five
minutes in the following solution:

Prepare the solutions separately and mix equal parts for use, at
the time of employment. Dry the plates in the dark, and keep in
the dark until used. Printing is done in the sun, and a vigorous
negative must be used, says the Moving Picture World. Exposure,
20 to 30 minutes. Wash 10 minutes in running water and dry. Brown
or purple tones may be had by sensitizing with the following
solution instead of the above:

Bathe the plates 5 minutes, keeping the fingers out of the
solution, to avoid blackened skin. Dry in the dark. Print to
bronzing under a strong negative; fix in hypo, toning first if
desired.

A Substitute for a Ray Filter

Not many amateur photographers possess a ray filter. A good
substitute is to use the orange glass from the ruby lamp. This
can be held in position in front of the lens with a rubber band.
A longer exposure will be necessary, but good cloud effects can
be procured in this manner.

Electric Lamp Experiments

Incandescent electric lamps can be made to glow so that they may
be seen in a dark room by rubbing the globe on clothing or with a
paper, leather or tinfoil and immediately holding near a 1/2-in.
Ruhmkorff coil which is in action but not sparking. The miniature
16 cp., 20 and 22-volt lamps will show quite brilliantly, but the
110-volt globes will not glow. When experimenting with these
globes everything should be dry. A cold, dry atmosphere will give
best results.

Annual Regatta, Port Melbourne, Australia

How to Make a Simple Wireless Telegraph
By Arthur E. Joerin

For Distances up to 1000 Feet

An efficient wireless-telegraph receiving apparatus for distances
up to 1,000 ft. may be constructed in the following manner:
Attach a watchcase telephone receiver to a dry cell, or battery,
of any make. The negative pole, or zinc, of the cell is connected
to a ground wire. This is done by attaching to a gas or water
pipe. The positive pole, or carbon, of the cell is connected to
the aerial line. This aerial collector can be made in various
ways, either by using a screen wire or numerous wires made in an
open coil and hung in the air. File a V-shaped groove in the
upper end of the carbon of the cell. Attach a small bent copper
wire in the binding post that is attached to the zinc of the
cell. In the bend of this wire and the V-shaped groove filed into
the carbon, lay a needle. This will complete the receiving
station. Use a spark coil in connection with a telegraph key for
the sending station, making a ground with one wire, and have the
other connected with another aerial line.

By connecting the telephone receiver to the cell and at the same
time having a short circuit a receiving station is made. As the
telephone offers a high resistance, part of the current will try
to take the shorter high resistance through the needle. If the
waves strike across the needle, the resistance is less, and thus
less current travels through the telephone receiver. If the wave
ceases, the resistance between the needle and the carbon is
increased, and as less current will flow the short way, it is
compelled to take the longer metallic way through the windings of
the receiver, which will cause the clickings that can be heard.

To Preserve Putty

Putty, when left exposed to the air, will soon become dry and
useless. I have kept putty in good condition for more than a year
by placing it in a glass jar and keeping it entirely covered with
water.

How to Make a Small Storage Battery

The cell of a storage battery consists of two plates, a positive
and a negative, made of lead
and placed in a dilute solution of
sulphuric acid. Large batteries made of large cells have a great
number of plates, both positive and negative, of which all
positive plates are connected to one terminal and the negative
plates to the other terminal. The storage cell, as described
below, is the right size to be charged by a few gravity cells and
is easily made.

Secure a piece of 1-3/4-in. lead pipe,
5 in. long, and cut both
ends smooth and square with the pipe. Solder a circular disk of
lead to one end, forming a cup of
the pipe. As this cup must hold
the sulphuric acid it must be perfectly liquid-tight.

It is also necessary to get another
lead pipe of the same length
but only 3/4 in. in diameter. In this pipe should be bored as
many 1/8 in. holes as possible, except for about 1 in. on each
end. One end of this tube is hammered together as shown at A in
the sketch to make a pocket to hold the paste. This, of course,
does not need to be watertight.

A box of wood is made to hold the larger tube or cup. This box
can be square, and the corners left open around the cup can be
filled with sawdust. A support is now made from a block of wood
to hold the tube, B, in place and to keep it from touching the
cup C. This support or block, D, is cut circular with the same
diameter as the lead cup C.
The lower portion of the block is cut
away so it will just fit inside of the cup to form a stopper. The
center of this block is now bored to make a hole the same size as
the smaller lead pipe.
Place the lead pipe in the hole and
immerse it in smoking hot paraffine wax, and leave it until the
wood has become thoroughly saturated with the hot wax. Use care
to keep the wax from running on the lead at any place other than
the end within the wood block. Two binding-posts should be
attached, one to the positive, or tube B, and the other to the
negative, or tube C, by soldering the joint.

A paste for the positive plate is made from 1 part sulphuric acid
and 1 part water with a sufficient amount of red
lead added to
make of thick dry consistency. When mixing the acid and water, be
sure to add the acid to the water and not the water to the acid.
Also remember that sulphuric acid
will destroy anything that it
comes in contact with and will make a painful burn if it touches
the hands. Stir the mixture with a stick and when a good dry
paste is formed, put it into the smaller tube and ram it down
until the tube is almost filled. The paste that may have come
through the holes is scraped off and the tube set aside to dry.
The large tube or cup is filled with a diluted solution of
sulphuric acid.
This solution should be about one-twelfth acid.
The cell is now complete and ready for storing the current. The
cell may be charged with three gravity cells. These are connected
in series and the positive terminal binding-post on the storage
cell is connected to the wire leading from the copper plate in
the gravity cell. The other plate is connected to the zinc. The
first charge should be run into the cell for about one week and
all subsequent charges should only take from 10 to 12 hours.

Fitting a Plug in Different Shaped Holes

Fits Four Different Shaped Holes

A certain king offered to give the prince his liberty if he could
whittle a plug that would fit four different shaped holes,
namely: a square hole, a round one, an oblong one and a
triangular one, says the Pathfinder. A broomstick was used to
make the plug and it was whittled in the shape shown in Fig. 1.
The holes in the different places as shown in Fig. 2, were fitted
by this one plug.

How to Make a Lightning Arrester

Secure a piece of wood about 3-1/2 in. square that will furnish a
nice finish and round the corners and make a small rounding edge
as shown in the sketch. From a piece of brass 1/16 in. thick cut
two pieces alike, A and B, and match them together, leaving about
1/16 in. between their upper edges and fasten them to the wood
with binding-posts. The third piece of brass, C, is fitted
between the pieces A and B allowing a space of 1/16-in. all
around the edge. One binding-post and a small screw will hold
the piece of brass, C, in place on the wood. The connections are
made from the line wires to the two upper binding-posts and
parallel from the lower binding-posts to the instrument. The
third binding-post on C is connected to the ground wire. Any
heavy charge from lightning will jump the saw teeth part of the
brass and is grounded without doing harm to the instruments used.

Contributed by Edwin Walker, Chicago, Ill.

A Home-Made Punt

Easy to Build and Safe to Use

A flat bottom boat is easy to make and is one of the safest
boats, as it is not readily overturned. It has the advantage of
being rowed from either end, and has plenty of good seating
capacity.

This punt, as shown in Fig. 1, is built 15 ft. long, about 20 in.
deep and 4 ft. wide. The ends are cut sloping for about 20 in.
back and under. The sides are each made up from boards held
together with battens on the inside of the boat near the ends and
in the middle. One wide board should be used for the bottom
piece. Two pins are driven in the top board of each side to serve
as oarlocks.

The bottom is covered with matched boards not over 5 in. wide.
These pieces are placed together as closely as possible, using
white lead
between the joints and nailing them to the edges of
the side boards and to a keel strip that runs the length of the
punt, as shown in Fig. 2. Before nailing the boards place lamp
wicking between them and the edges of the side boards. Only
galvanized nails should be used. In order to make the punt
perfectly watertight it is best to use the driest lumber
obtainable. At one end of the punt a skag and a rudder can be
attached as shown in Fig. 3.

Photographers’ Printing Frame Stand

Adjustable to Any Height

When using developing papers it is always bothersome to build up
books or small boxes to make a place to set the printing frame in
front of the light. Details for making a small stand that is
adjustable to any desired height are shown in the sketch. In Fig.
1 is shown the construction of the sliding holder. A piece of
1/4-in. gas pipe, A, is cut 1 in. long and fitted with a
thumbscrew, B. The piece of pipe is soldered to the middle on the
back side of a piece of metal that is about 4 by 4-1/2 in. with
its lower edge turned up to form a small shelf as shown at C. The
main part of the stand is made by inserting a 5/16-in. rod
tightly into a block of hard maple wood that is 1 in. thick and
3-1/2 in. square (Fig 2). The pipe that is soldered to the metal
support will slide up and down the rod and the thumbscrew can be
set to hold it at the desired point.

Heat and Expansion

Take an electric light bulb from which the air has not been
exhausted and immerse it in water and then break off the point.
As there is a vacuum in the bulb it will quickly fill with water.
Shake the bulb gently until a part of the water is out and then
screw the bulb into a socket with the point always downward.
Apply the current and the heated air inside will soon expand and
force the water out with great rapidity. Sometimes this
experiment can be done several times by using the same bulb.

Contributed by Curtiss Hill, Tacoma, Wash.

Photographing a Streak of Lightning

The accompanying illustration is a remarkable photograph of a
streak of lightning. Many interesting pictures of this kind can
be made during a storm at night. The camera is set in a place
where it will not get wet and left standing with the shutter open
and the plate ready for the exposure. Should a lightning streak
appear within the range of the lens it will be made on the plate,
which can be developed in the usual manner. It will require some
attention to that part of the sky within the range of the lens so
as to not make a double exposure by letting a second flash enter
the open lens.

Contributed by Charles H. Wagner.

How to Make a Small Single-Phase Induction Motor
By C. H. Bell

The following notes on a small single-phase induction motor,
without auxiliary phase, which the writer has made, may be of
interest to some of our readers, says the Model Engineer. The
problem to be solved was the construction of a motor large enough
to drive a sewing machine or very light lathe, to be supplied
with 110-volt alternating current from a lighting circuit, and to
consume, if possible, no more current than a 16-cp. lamp. In
designing, it had to be borne in mind that, with the exception of
insulated wire, no special materials could be obtained.

The principle of an induction motor is quite different from that
of the commutator motor. The winding of the armature, or “rotor,”
has no connection with the outside circuit, but the current is
induced in it by the action of the alternating current supplied
to the winding of the field-magnet, or “stator.” Neither
commutator nor slip rings are required, and all sparking is
avoided. Unfortunately, this little machine is not self-starting,
but a slight pull on the belt just as the current is turned on is
all that is needed, and the motor rapidly gathers speed provided
no load is put on until it is in step with the alternations of
the supply. It then runs at constant speed whether given much or
little current, but stops if overloaded for more than a few
seconds.

The stator has four poles and is built up of pieces of sheet iron
used for stove pipes, which runs about 35 sheets to the inch. All
the pieces are alike and cut on the lines with the dimensions as
shown in Fig. 1, with the dotted line, C, to be filed out after
they are placed together. Each layer of four is placed with the
pointed ends of the pieces alternately to the right and left so
as to break joints as shown in Fig. 2. The laminations were
carefully built up on a board into which heavy wires had been
driven to keep them in place until all were in position and the
whole could be clamped down. In the middle of the pieces 1/4-in.
holes, B, were then drilled and 1/4-in. bolts put in and
tightened up, large holes being cut through the wood to enable
this to be done. The armature tunnel was then carefully filed out
and all taken apart again so that the rough edges could be
scraped off and the laminations given a thin coat of shellac
varnish on one side. After assembling a second time, the bolts
were coated with shellac and put into place for good. Holes 5-32
in. in diameter were drilled in the corners, A, and filled with
rivets, also varnished before they were put in. When put together
they should make a piece 2 in. thick.

This peculiar construction was adopted because proper stampings
were not available, and as every bit of sheet iron had to be cut
with a small pair of tinners’ snips, it was important to have a
very simple outline for the pieces. They are not particularly
accurate as it is, and when some of them got out of their proper
order while being varnished, an awkward job occurred in the
magnet which was never entirely corrected. No doubt some energy
is lost through the large number of joints, all representing
breaks in the magnetic circuit, but as the laminations are
tightly held together and the circuit is about as compact as it
could possibly be, probably the loss is not as great as it would
appear at first sight.

The rotor is made of laminations cut from sheet iron, as shown in
Fig. 3, which were varnished lightly on one side and clamped on
the shaft between two nuts in the usual way. A very slight cut
was taken in the lathe afterwards to true the circumference. The
shaft was turned from 1/2-in. wrought iron, no steel being
obtainable, and is shown with dimensions in Fig. 4. The bearings
were cast of babbitt metal, as shown in Fig. 5, in a wooden mold
and bored to size with a twist drill in the lathe. They are
fitted with ordinary wick lubricators. Figures 6 and 7 are
sections showing the general arrangement of the machine.

The stator is wound full with No. 22 double cotton-covered copper
wire, about 2-1/2 lb. being used, and the connections are such as
to produce alternate poles—that is, the end of the first coil is
joined to the end of the second the beginning of the second to
the beginning of the third, and the end of the third to the end
of the fourth, while the beginnings of the first and fourth coils
connect to the supply.

The rotor is wound with No. 24 double cotton-covered copper wire,
each limb being filled with about 200 turns, and all wound in the
same direction. The four commencing ends are connected together
on one side of the rotor and the four finishing ends are soldered
together on the other. All winding spaces are carefully covered
with two layers of cambric soaked in shellac, and as each layer
of wire was wound, it was well saturated with varnish before the
next was put on.

This type of motor has drawbacks, as before stated, but if
regular stampings are used for the laminations, it would be very
simple to build, having no commutator or brushes, and would not
easily get out of order. No starting resistance is needed, and as
the motor runs at constant speed, depending upon the number of
alterations of the supply, a regulating resistance is not needed.

Carbolic Acid Burns

The pain of carbolic acid burns can be relieved promptly by
washing with alcohol, if applied immediately. If too late for
alcohol to be of use, brush with water containing saturated
solution of picric acid.

How to Make a Paper Book Cover

To Protect Book Covers

Book covers become soiled in handling and especially school
books. Various methods are applied for making a temporary cover
that will protect the book cover. A paper cover can be quickly
made by using a piece of paper larger than both covers on the
book when they are open. Fold the paper on the long dotted line,
as shown in Fig. 1. When the folds are made the paper should then
be just as wide as the book cover is high. The ends are then
folded on the short dotted lines, which will make it appear as
shown in Fig. 2. The paper thus folded is placed on the book
cover as shown in Fig. 3.

Contributed by C. E. McKinney, Jr., Newark, N. J.

How to Make Lantern Slides

The Camera as It is Arranged in Front of the Window for Reducing
the Size of a Picture, and the Method of Binding the Slides

The popularity of lantern slides, and especially of colored ones,
as a means of illustrating songs, has caused so large a demand
for this class of work that almost any amateur may take up slide
making at a good profit. The lantern slide is a glass plate,
coated with slow and extremely fine-grained emulsion. The size is
3-1/4 by 4 in. A lantern slide is merely a print on a glass plate
instead of on paper. Lantern slides can be made in two different
ways. One is by contact, exactly the same as a print is made on
paper, and the other by reduction in the camera. In making slides
by contact, select the negative and place it in the printing
frame and put the lantern plate upon it, film to film. Clamp down
the back and expose just as in making a print. A good method of
exposing is to hold a lighted match about 3 in. from the frame
for three or more seconds according to the density.

Development is carried on in the same manner as with a negative.
The image should appear in. about a minute, and development
should be over in three or four minutes. If the exposure has been
correct, the high lights will stay white throughout the
development and will come out as clear glass after fixing. It is
best to use the developers recommended by the manufacturer of the
plates used, the formulas being found in each package of plates.
It is best, also, to use a plain fixing bath, which must be fresh
and kept as cool as possible in hot weather.

The lantern-slide film that is new on the market can be handled
in the same manner as the glass-plate slide, except that the
binding is different. The results are the same and the slides are
not so bulky to handle. Being unbreakable, they are much used by
travelers. The manner of binding them for use in a lantern is
described on the circular enclosed with the film.

When the negative is larger than the lantern-slide plate, and it
is desirable to reduce the entire view upon the slide, a little
extra work will be necessary. Select a room with one window, if
possible, and fit a light-proof frame into it to keep out all
light with the exception of a hole in which to place the
negative, as shown in Fig. 1. Unless this hole is on a line with
the sky it will be necessary to place a sheet of white cardboard
at an angle of 45 deg. on the outside of the frame to reflect the
light through the negative as shown in Fig. 2. Make or secure an
inside kit to place in the plate holder of your camera to hold
the lantern slide plate as shown in Fig. 3. Draw lines with a
pencil, outlining on the ground glass of the camera the size of
the lantern slide plate, and in the place where the plate will be
in the plate holder when placed in position in the camera. This
will enable you to focus to the proper size. Place the camera in
front of the hole in the frame, place the negative in the hole
and focus the camera for the lantern slide size. Expose with a
medium stop for about 20 seconds and treat the plate the same as
with the contact exposure.

When dry the lantern slide plate may be tinted any color by means
of liquid colors. These can be purchased from any photo material
store. In coloring the slide plate it is only necessary to
moisten the gelatine film from time to time with a piece of cloth
dampened in water. The colors may then be spread evenly with a
soft brush, which should be kept in motion to prevent spots. The
slide is put together by placing a mat made of black paper, as
shown in Fig. 4, on the gelatine side of the lantern slide, A,
Fig. 5, and then a plain glass, B, over the mat, C, and the three
bound together with passe-partout tape, D. Contrasty negatives
make the best slides, but the lantern slide plate should be made
without any attempt to gain density.

How To Make A Porch Swing Chair

The material needed for making this porch swing chair are two
pieces of round wood 2-1/2 in. in diameter and 20 in. long, and
two pieces 1-1/4 in. in diameter and 40 in. long. These longer
pieces can be made square, but for appearance it is best to have
them round or square with the corners rounded. A piece of canvas,
or other stout cloth, 16 in. wide and 50 in. long, is to be used
for the seat. The two short pieces of wood are used for the ends
of the chair and two 1-in. holes are bored in each end of them
1-1/2 in. from the ends, and between the holes and the ends
grooves are cut around them to make a place to fasten ropes, as
shown at B, Fig. 1. The two longer pieces are used for the sides
and a tenon is cut on each end of them to fit in the 1-in. holes
bored in the end pieces, as shown at A, Fig. 1. The canvas is now
tacked on the end pieces and the pieces given one turn before
placing the mortising together.

The chair is now hung up to the porch ceiling with ropes attached
to a large screw eye or hook. The end of the chair to be used for
the lower part is held about 16 in. from the floor with ropes
direct from the grooves in the end pieces to the hook. The upper
end is supported by using a rope in the form of a loop or bail,
as shown in Fig. 2. The middle of the loop or bail should be
about 15 in. from the end piece of the chair. Another rope is
attached to the loop and through the hook and to a slide as
shown. This will allow for adjustment to make the device into a
chair or a hammock.

Contributed by Earl R. Hastings, Corinth, Vt.

How to Find the Blind Spot in the Eye

Make a small black circular dot 1/2 in. in diameter on a piece of
cardboard and about 3 in. from the center of this dot draw a
star. Hold the cardboard so that the star will be directly in
front of one eye, while the dot will be in front of the other. If
the star is in front of the left eye, close the right eye and
look steadily at the star while you move the cardboard until the
point is reached where the dot disappears. This will prove the
presence of a blind spot in a person’s eye. The other eye can be
given the same experiment by turning the cardboard end for end.
The blind spot does not indicate diseased eyes, but it simply
marks the point where the optic nerve enters the eyeball, which
point is not provided with the necessary visual end organs of the
sight, known as rods and cones.

Beeswax Substitute

A wax from the rafie palm of Madagascar is being used as a
substitute for beeswax.

Home-Made Water Wheel Does Family Washing

The accompanying sketch illustrates a very ingenious device which
does the family washing, as well as to operate other household
machines. A disk 1 in. in thickness and 10 in. in diameter was
cut from a piece of rough board, and on its circumference were
nailed a number of cup-shaped pieces cut from old tin cans. A
hole was then bored through the center of the disk and an old
piece of iron rod was driven through to form a shaft. Two holes
were then bored opposite each other through the sides of a wooden
box in which the disk was placed, allowing the shaft to project
through the holes. A small grooved wooden pulley was driven
tightly on one of the projecting ends of the shaft. The top of
the box was then tightly closed and a hole, large enough to admit
the nozzle of a garden hose, was bored so that the jet of water
would flow upon the tin buckets that were nailed to the
circumference of the wheel or disk. Another hole was bored in the
bottom of the box large enough to allow the waste water to run
away freely. A belt, made from an ordinary sash cord, was run
from the small pulley on the waterwheel to a large pulley, as
shown in Fig. 1. A pitman was attached to the large pulley, which
operates the washing machine by its reciprocating motion, and the
length of the stroke is adjusted by moving the position of the
hinge joint on the arm of the washing machine, as shown in Fig.
2. The pressure at the nozzle is about 20 lb. per square inch,
and is sufficient to drive the waterwheel under all ordinary
circumstances.

Contributed by P. J. O’Gara, Auburn, Cal,

An Optical Illusion

When looking at the accompanying sketch you will say that the
letters are alternately inclined to the right and left. They are
not so and can be proved by measuring the distance of the top and
bottom of any vertical strokes from the edge of the entire block.
They will be found to be exactly the same distance. Or take any
of the horizontal strokes of the four letters and see how far
their extremities are from the top and bottom of the entire
block. It will be found that a line joining the extremities of
the strokes are strictly parallel to the top or bottom and that
they are not on a slant at all. It is the slant of the numerous
short lines that go to make up the letter as a whole that
deceives the eye.

Home-Made Micrometer

It often becomes necessary to find the thickness of material so
thin, or inconvenient to measure, that a rule or other measuring
device will not serve the purpose. A simple, fairly accurate, and
easily made apparatus of the micrometer form may be constructed
as shown by the accompanying sketch. Secure a common iron or
brass bolt about 1/4-in. in diameter and about 2-1/2 in. long,
with as fine a thread as possible, and the thread cut to within a
short distance of the head of the bolt. The head of the bolts
should have a slot cut for the use of a screwdriver. Clamp
together two blocks of wood with square corners which are about 1
in. wide, 3/4 in. thick and 2-1/2 in. long and fasten them
together with small pieces nailed across the ends. The width of
the blocks will then be about 2 in. Bore a 1/4-in. hole through
the center of the blocks in the 2 in. direction. Remove the clamp
and set the nut into one of the blocks, so that the hole will be
continuous with the hole in the wood. Cut out a piece from the
block combination, leaving it shaped like a bench, and glue the
bottoms of the legs to a piece of thin board about 2-1/2 in.
square for a support.

Solder one end of a stiff wire that is about 2 in. long to the
head of the bolt at right angles to the shaft, and fix a disc of
heavy pasteboard with a radius equal to the length of the wire,
and with its circumference graduated into equal spaces, to serve
in measuring revolutions of the end of the wire, to the top of
the bench. Put the bolt in the hole, screwing it through the nut,
and the construction is complete. The base is improved for the
measuring work by fastening a small piece of wood on the board
between the legs of the bench. A small piece of metal is glued on
this piece of wood at the point where the bolt meets it.

Find the number of threads of the screw to the inch by placing
the bolt on a measuring rule, and counting the threads in an inch
of its length. The bolt in making one revolution will descend a
distance equal to the distance between the threads.

The device is used by placing the object whose thickness is to be
measured on the base under the bolt, and screwing the bolt down
until its end just touches the object, then removing the object,
and screwing the bolt down until its end just touches the base,
carefully noting while doing so the distance that the end of the
wire moves over the scale. The part of a rotation of the bolt, or
the number of rotations with any additional parts of a rotation
added, divided by the number of threads to the inch, will be the
thickness of the object. Quite accurate measurements may be made
with this instrument, says the Scientific American, and in the
absence of the expensive micrometer, it serves a very useful
purpose.

Another Electric Lamp Experiment

Break a portion of the end off from a 16-cp. globe that has been
thrown away as useless. Shake the globe until all the filament
is broken away, leaving only the ends of the platinum wire
exposed. Screw the globe into a socket that sets upright and fill
it with salt water. Make one connection to the socket from the
positive wire of a 110 volt circuit and the other to a ground.
When the current is turned on small stars will be seen in the
globe, which show up fine at night.

Contributed by Lindsay McMillan, Santa Maria, Oal.

Removing Ink Stains

Two or three applications of milk which are wiped up with a dry
cloth will remove india ink spots on carpets.

Feat of Balancing on Chairs

Among the numerous physical exercises is the feat of balancing on
the two rear legs of a chair while one foot rests on the front
part of the seat and the other on the back of the chair. This
may appear to be a hard thing to do, yet with a little practice
it may be accomplished. This exercise is one of many practiced by
the boys of a boys’ home for an annual display given by them. A
dozen of the boys will mount chairs at the same time and keep
them in balance at the word of a commanding officer.

How to Make a Merry-Go-Round Swing

Side and Top View

A 6 by 6-in. piece of wood 12 ft. long is used for the center
pole. Bore a 3/4-in. hole in each end to a depth of 6 in. Place a
3/4-in. bolt in each hole, the bolt being long enough to protrude
2 in. beyond the end of the wood. Short pieces of wood are nailed
on the center pole about 2 ft. from the end that is to be used
for the bottom. This should form a hub on which to place the
inner ends of the extending spokes that hold the platform. The
spokes are made from twelve pieces of 2 by 4-in. material 12 ft.
long.

Usually a wheel can be found in a scrap pile suitable to place on
the pin that is in the top end of the center pole. The wheel
should be open or have spokes. This wheel is used to attach wires
for guying. The bottom pin in the center pole is placed in a hole
that is bored into a block of wood about 12-in. square and 3 or 4
in. thick. A piece of sheet metal should be drilled and placed on
the pin between the block and end of the pole to make a smooth
bearing. The center pole is now placed in position and guyed with
six wires that are about 35 ft. long. Stakes are driven into the
ground and the wires fastened to them and to the wheel at the top
end of the pole. Care should be taken when attaching the wires to
get the center pole to stand perpendicular. Twelve hooks should
be placed at equal distances around the center pole about 1 ft.
from the top end. Wires are fastened to these hooks and to the
twelve 2 by 4-in. pieces used for the spokes. The wires should be
tied around each spoke about 2 ft. from the ends. Space the
spokes with equal divisions and cover the outer 2 ft. of the ends
with boards, as shown in the plan sketch on the right hand end of
the drawing. The boards may be nailed or bolted. If bolted and
the wires made in a loop at the hooks, the swing can easily be
taken apart and changed from one place to another.

Contributed by A. O. Graham, Fort Worth, Tex.

Home-Made Arc Lamp

The frame of the lamp is made from bar metal 3/4 in. wide and 1/8
in. thick, bent and welded to make a continuous loop in the shape
as shown at G in the sketch. This frame should be about 10-1/2
in. long with the upper or wider part 4 in. long, and the lower
part 6-1/2 in. long. The width should be about 5-1/4 in. at the
top and 4 in. at the bottom. A cross bar, L, made of the same
material, is fitted into the off-set in the frame and riveted.
Holes are drilled through the frame and brass bushings, H and J,
are fitted for bearings to receive the adjusting brass rod, B,
which should be 1/4 in. in diameter. A brass curtain rod can be
used for the rod B, and on its lower end a socket, P, is
soldered.

A piece of brass 2 in. long, 1/2 in. wide and 1/8 in. thick is
used for the armature, A, to be operated by the magnet coil, C.
The coil, C, is made in the usual manner by wrapping No. 14
cotton-covered magnet wire on a wooden spool that has a soft iron
core. The spool is about 2-1/2 in. long. The armature, A, is
drilled, making a hole just a little larger than the rod, B, and
is adjusted in place by two set screws, D and E. A soft piece of
iron, F, is fastened to the opposite end of the armature with a
screw, which should be placed directly under the end of the
coil’s core. This end of the armature may be kept from swinging
around by placing it between a U-shaped piece of brass fastened
to the cross piece L. At the bottom end of the frame, and
directly centering the holes H and J, a hole is drilled to
receive a hard rubber bushing, R, for insulating the brass
ferrule, S, that holds the lower carbon.

One connection is made from the main to the upper binding-post,
which is in turn connected to one terminal of the coil, C, the
other coil terminal being attached to the frame. The other main
connection is made to the lower binding-post, which is also
connected to the brass ferrule, S, by soldering. The two
binding-posts are insulated from the frame the same as the
ferrule S. When using on a 110-volt circuit there must be some
resistance in connection, which may be had by using German silver
wire, or a water rheostat heretofore described.

Contributed by Arthur D. Bradley. Randolph, Mass.

Irrigation

The Mexican government has appropriated $25,000,000 for
irrigation work.

How to Hang Your Hat on a Lead Pencil

Take a smooth hexagon lead pencil, one without either rubber or
metal end, and place it against a door or window casing; then
with a firm, heavy pressure slide the pencil some 3 or 4 in. and
it will stay as if glued to the casing. You may now hang your hat
on the end of the pencil.

When you slide the pencil along the casing, do it without any
apparent effort, and it will appear to your audience as though
you had hypnotized it. This is a very neat trick if performed
right. Figure 1 shows the pencil on the casing and Fig. 2 the hat
hanging on it.

Tying a Knot for Footballs

A Secure Knot

One of the most prominent English football clubs kept the tying
of this knot on the rubber hose of their football a secret and
never allowed all of its members to know how it was tied. This
tie can be used on grain sacks, and in numerous other like
instances. Make one loop in the cord and then another exactly the
same way, as shown in Fig. 1, placing the end of the cord under
the first loop, then pulling at each end of the cord as in Fig.
2.

A.E.J.

Stove Polish

Stove polish consists of 2 parts graphite, 4 parts copperas and 2
parts bone black, mixed with water to form a paste.

How to Give an Electric Shock While Shaking Hands

Details of Induction Coil

There is nothing quite so startling as to receive an electric
shock unexpectedly and such a shock may be given to a friend
while shaking hands upon meeting. The shock produced is not
harmful and the apparatus can be carried in the pocket. It
consists of a small induction coil that can be constructed at
home.

The core of the coil, A, Fig. 1, is constructed in the usual
manner, of small soft-iron wire to make a bundle about 3/16 in.
in diameter and 2 in. long. The coil ends are made from
cardboard, about 1 in. in diameter, with a 3/16-in. hole in the
center. The hole should be cut as shown in Fig. 2, so as to have
four small pieces that can be bent out, leaving the projections
as shown. After wrapping three or four turns of paper around the
bundle of wires the cardboard ends are put on with the
projections inside, so the coils of wire will hold them in place.
About 70 turns of No. 24 gauge double covered magnet wire is
first placed on the core, for the primary, and then 1,500 turns
of No. 32 or 34 gauge double-covered wire is wrapped on top of
the primary, for the secondary. Sufficient length of wire must be
left outside at each end of both windings to make connections.
The vibrator B, Fig. 1, and the support C are made from thin
spring steel, about 1/8 in. wide, bent as shown and securely
fastened to the cardboard end of the coil. The armature is made
from a soft piece of iron, about 3/16 in. in diameter and 1/16
in. thick, which is soldered to the end of the vibrator directly
opposite the end of the core. A small screw is fitted in the end
of the support, C, for adjustment, which should be tipped with
platinum and also a small piece of platinum placed where the
screw will touch the vibrator, B.

One of the primary wires is connected to the screw support. The
vibrator, is connected to a flash lamp battery, D. The other
primary wire is connected to a switch, S, which in turn is
connected to the other terminal of the battery. The switch, S,
may be made from a 3/8-in. cork with the wires put through about
3/16 in. apart and allow them to project about 1/2 in. The plate
E is cut about 1/2 in. square from a piece of copper and is
fastened to the heel of one shoe and connected with a wire from
the secondary coil which must be concealed inside of the trouser
leg. The other secondary wire is connected through the coat
sleeve to a finger ring, F. The vibrator screw must be properly
adjusted. When the vibrator is not working the armature should be
about 1/16 in. from the core and directly opposite.

The coil when complete will be about 2-1/2 in. long and 1 in. in
diameter. The coil can be placed in an old box that has been used
for talcum powder or shaving stick. The space around the coil in
the box can be filled with paper to keep it tight.

The coil and battery are carried in the pockets and the cork
button put in the outside coat pocket, where it can be pressed
without attracting attention.

Experiment with Heat

Place a small piece of paper, lighted, in an ordinary water
glass. While the paper is burning turn the glass over and set
into a saucer previously filled with water. The water will
rapidly rise in the glass, as shown in the sketch.

How to Attach a Combination Trunk Lock

A small combination lock for chests can be purchased for a small
sum of money and attached to a trunk cover after first removing
the old lock as shown in Fig. 1. It is necessary to add 1/2-in.
to the thickness of the trunk lid or cover. This may be done by
placing a brass plate 1/8-in. thick on the outside and a board
3/8-in. thick on the inside. The lock, brass plate, board and
trunk cover are all securely riveted together. The support for
the dial is soldered to the brass plate.

The hasp, if that be the name for the double toothed arrangement
that catches into the lock, was to be secured by only three brass
screws, which seemed to be insufficient, says a correspondent of
the Metal Worker; therefore a piece of heavy tin was formed over
the front of the trunk, which is only 3/8-in. board, the hasp
tinned and soldered to the back of the now U-shaped tin, and the
tin placed over the board and all fastened in position. The tin
is 4 in. wide, 16 in. long and when placed over the board, it
laps down about 8 in. between the boards, and the same distance
inside of the new board, as shown by the heavy line in the cross
section, Fig. 1. Wrought nails are used which pass twice through
the tin and both boards, and then well clinched. The three screws
were then put in the hasp.

The knob on the dial extends out too far, which may be filed off
and two holes substituted, as shown, with which to operate the
dial. An old key is filed down in the shape shown in Fig. 2 to
fit the two holes. As the dial is convex it will need protection
to prevent injury by rough handling. A leather shield may be used
for this purpose, which is cut with two holes, one for the key
and the other to permit the operator to observe the numbers on
the dial. The shield answers a further purpose of preventing any
bystander from noting the numbers on the dial.

An Electric Illusion Box

Construction of Magic Boxes

Four Electric Magic Boxes Complete for Use

The accompanying engravings show a most interesting form of
electrically operated illusion consisting of a box divided
diagonally and each division alternately lighted with an electric
lamp. By means of an automatic thermostat arranged in the lamp
circuit causing the lamps to light successively, an aquarium
apparently without fish one moment is in the next instant
swarming with live gold fish; an empty vase viewed through the
opening in the box suddenly is filled with flowers, or an empty
cigar box is seen and immediately is filled with cigars.

These electric magic boxes as shown are made of metal and
oxidized copper finished, but for ordinary use they can be made
of wood in the same shape and size. The upper magic boxes as are
shown in the engraving are about 12 in. square and 8-1/2 in. high
for parlor use and the lower boxes are 18 in. square and 10-1/2
in. high for use in window displays. There is a partition
arranged diagonally in the box as shown in the plan view, which
completely divides the box into two parts. One-half the partition
is fitted with a plain, clear glass as shown. The partition and
interior of the box are rendered non-reflecting by painting with
a dull, not shiny, black color. When making of wood, a door must
be provided on the side or rear to make changes of exhibits. If
the box is made large enough, or in the larger size mentioned,
openings may be made in the bottom for this purpose, and also
used in case of performing the magic trick of allowing two
persons to place their heads in the box and change from one to
the other. The electric globes are inserted as shown at LL
through the top of the box, one in each division. When the rear
part is illuminated, any article arranged within that part will
be visible to the spectator looking into the box through the
front opening, but when the front part is illuminated, and the
back left dark, any article placed therein will be reflected in
the glass, which takes the same position to the observer as the
one in the rear. Thus a plain aquarium is set in the rear part
and one with swimming fish placed in the front, and with the
proper illumination one is changed, as it appears, into the
other. When using as a window display, place the goods in one
part and the price in the other. Many other changes can be made
at the will of the operator.