SCIENTIFIC AMERICAN SUPPLEMENT NO. 647

NEW YORK, MAY 26, 1888

Scientific American Supplement. Vol. XXV., No. 647.

Scientific American established 1845

Scientific American Supplement, $5 a year.

Scientific American and Supplement, $7 a year.

INFLUENCE MACHINES.¹

By Mr. James Wimshurst.

I have the honor this evening of addressing a few remarks to you
upon the subject of influence machines, and the manner in which I
propose to treat the subject is to state as shortly as possible,
first, the historical portion, and afterward to point out the
prominent characteristics of the later and the more commonly known
machines. The diagrams upon the screen will assist the eye to the
general form of the typical machines, but I fear that want of time
will prevent me from explaining each of them.

In 1762 Wilcke described a simple apparatus which produced
electrical charges by influence, or induction, and following this
the great Italian scientist Alexander Volta in 1775 gave the
electrophorus the form which it retains to the present day. This
apparatus may be viewed as containing the germ of the principle of
all influence machines yet constructed.

Another step in the development was the invention of the doubler
by Bennet in 1786. He constructed metal plates which were thickly
varnished, and were supported by insulating handles, and which were
manipulated so as to increase a small initial charge. It may be
better for me to here explain the process of building up an
increased charge by electrical influence, for the same principle
holds in all of the many forms of influence machines.

This Volta electrophorus, and these three blackboards, will
serve for the purpose. I first excite the electrophorus in the
usual manner, and you see that it then influences a charge in its
top plate; the charge in the resinous compound is known as
negative, while the charge induced in its top plate is known as
positive. I now show you by this electroscope that these charges
are unlike in character. Both charges are, however, small, and
Bennet used the following system to increase them.

Let these three boards represent Bennet’s three plates. To plate
No. 1 he imparted a positive charge, and with it he induced a
negative charge in plate No. 2. Then with plate No. 2 he induced a
positive charge in plate No. 3. He then placed the plates Nos. 1
and 3 together, by which combination he had two positive charges
within practically the same space, and with these two charges he
induced a double charge in plate No. 2. This process was continued
until the desired degree of increase was obtained. I will not go
through the process of actually building up a charge by such means,
for it would take more time than I can spare.

Fig. 11.

Fig. 12.

In 1787 Carvallo discovered the very important fact that metal
plates when insulated always acquire slight charges of electricity;
following up those two important discoveries of Bennet and
Carvallo, Nicholson in 1788 constructed an apparatus having two
disks of metal insulated and fixed in the same plane. Then by means
of a spindle and handle, a third disk, also insulated, was made to
revolve near to the two fixed disks, metallic touches being fixed
in suitable positions. With this apparatus he found that small
residual charges might readily be increased. It is in this simple
apparatus that we have the parent of influence machines (see Fig.
1), and as it is now a hundred years since Nicholson described this
machine in the Phil. Trans., I think it well worth showing a large
sized Nicholson machine at work to-night (see Fig. 11, above).

In 1823 Ronalds described a machine in which the moving disk was
attached to and worked by the pendulum of a clock. It was a
modification of Nicholson’s doubler, and he used it to supply
electricity for telegraph working. For some years after these
machines were invented no important advance appears to have been
made, and I think this may be attributed to the great discoveries
in galvanic electricity which were made about the commencement of
this century by Galvani and Volta, followed in 1831 to 1857 by the
magnificent discoveries of Faraday in electro-magnetism,
electro-chemistry, and electro-optics, and no real improvement was
made in influence machines till 1860, in which year Varley patented
a form of machine shown in Fig. 2. It also was designed for
telegraph working.

In 1865 the subject was taken up with vigor in Germany by
Toepler, Holtz, and other eminent men. The most prominent of the
machines made by them are figured in the diagrams (Figs. 3 to 6),
but time will not admit of my giving an explanation of the many
points of interest in them; it being my wish to show you at work
such of the machines as I may be able, and to make some
observations upon them.

In 1866 Bertsch invented a machine, but not of the multiplying
type; and in 1867 Sir William Thomson invented the form of machine
shown in Fig. 7, which, for the purpose of maintaining a constant
potential in a Leyden jar, is exceedingly useful.

The Carre machine was invented in 1868, and in 1880 the Voss
machine was introduced, since which time the latter has found a
place in many laboratories. It closely resembles the Varley machine
in appearance, and the Toepler machine in construction.

In condensing this part of my subject, I have had to omit many
prominent names and much interesting subject matter, but I must
state that in placing what I have before you, many of my scientific
friends have been ready to help and to contribute, and, as an
instance of this, I may mention that Prof. Sylvanus P. Thompson at
once placed all his literature and even his private notes of
reference at my service.

I will now endeavor to point out the more prominent features of
the influence machines which I have present, and, in doing so, I
must ask a moment’s leave from the subject of my lecture to show
you a small machine made by that eminent worker Faraday, which,
apart from its value as his handiwork, so closely brings us face to
face with the imperfect apparatus with which he and others of his
day made their valuable researches.

The next machine which I take is a Holtz. It has one plate
revolving, the second plate being fixed. The fixed plate, as you
see, is so much cut away that it is very liable to breakage. Paper
inductors are fixed upon the back of it, while opposite the
inductors, and in front of the revolving plate, are combs. To work
the machine (1) a specially dry atmosphere is required; (2) an
initial charge is necessary; (3) when at work the amount of
electricity passing through the terminals is great; (4) the
direction of the current is apt to reverse; (5) when the terminals
are opened beyond the sparking distance, the excitement rapidly
dies away; (6) it does not part with free electricity from either
of the terminals singly.

It has no metal on the revolving plates, nor any metal contacts;
the electricity is collected by combs which take the place of
brushes, and it is the break in the connection of this circuit
which supplies a current for external use. On this point I cannot
do better than quote an extract from page 339 of Sir William
Thomson’s “Papers on Electrostatics and Magnetism,” which runs:
“Holtz’s now celebrated electric machine, which is closely
analogous in principle to Varley’s of 1860, is, I believe, a
descendant of Nicholson’s. Its great power depends upon the
abolition by Holtz of metallic carriers and metallic
make-and-break-contacts. It differs from Varley’s and mine by
leaving the inductors to themselves, and using the current in the
connecting arc.”

In respect to the second form of Holtz machine (Fig. 4) I have
very little information, for since it was brought to my notice
nearly six years ago I have not been able to find either one of the
machines or any person who had seen one. As will be seen by the
diagram, it has two disks revolving in opposite directions, it has
no metal sectors and no metal contacts. The “connecting arc
circuit” is used for the terminal circuit. Altogether I can very
well understand and fully appreciate the statement made by
Professor Holtz in Uppenborn’s Journal of May, 1881, wherein
he writes that “for the purpose of demonstration I would rather be
without such machines.”

The first type of Holtz machine has now in many instances been
made up in multiple form, within suitably constructed glass cases,
but when so made up, great difficulty has been found in keeping
each of the many plates to a like excitement. When differently
excited, the one set of plates furnished positive electricity to
the comb, while the next set of plates gave negative electricity;
as a consequence, no electricity passed the terminal.

To overcome this objection, to dispense with the dangerously cut
plates, and also to better neutralize the revolving plate,
throughout its whole diameter, I made a large machine having twelve
disks 2 ft. 7 in. in diameter, and in it I inserted plain
rectangular slips of glass between the disks, which might readily
be removed; these slips carried the paper inductors. To keep all
the paper inductors on one side of the machine to a like
excitement, I connected them together by a metal wire. The machine
so made worked splendidly, and your late president, Mr.
Spottiswoode, sent on two occasions to take note of my successful
modifications. The machine is now ten years old, but still works
perfectly. I will show you a smaller sized one at work.

The next machine for observations is the Carre (Fig. 8). It
consists essentially or a disk of glass which is free to revolve
without touch or friction. At one end of a diameter it moves near
to the excited plate of a frictional machine, while at the opposite
end of the diameter is a strip of insulting material, opposite
which, and also opposite the excited amalgam plate, are combs for
conducting the induced charges, and to which the terminals are
metallically connected; the machine works well in ordinary
atmosphere, and certainly is in many ways to be preferred to the
simple frictional machine. In my experiments with it I found that
the quantity of electricity might be more than doubled by adding a
segment of glass between the amalgam cushions and the revolving
plate. The current in this type of machine is constant.

The Voss machine has one fixed plate and one revolving plate.
Upon the fixed plate are two inductors, while on the revolving
plate are six circular carriers. Two brushes receive the first
portions of the induced charges from the carriers, which portions
are conveyed to the inductors. The combs collect the remaining
portion of the induced charge for use as an outer circuit, while
the metal rod with its two brushes neutralizes the plate surface in
a line of its diagonal diameter. When at work it supplies a
considerable amount of electricity. It is self-exciting in ordinary
dry atmosphere. It freely parts with its electricity from either
terminal, but when so used the current frequently changes its
direction, hence there is no certainty that a full charge has been
obtained, nor whether the charge is of positive or negative
electricity.

I next come to the type of machine with which I am more closely
associated, and I may preface my remarks by adding that the
invention sprang solely from my experience gained by constantly
using and experimenting with the many electrical machines which I
possessed. It was from these I formed a working hypothesis which
led me to make my first small machine. It excited itself when new
with the first revolution. It so fully satisfied me with its
performance that I had four others made, the first of which I
presented to this Institution. Its construction is of a simple
character. The two disks of glass revolve near to each other and in
opposite directions. Each disk carries metallic sectors; each disk
has its two brushes supported by metal rods, the rods to the two
plates forming an angle of 90 deg. with each other. The external
circuit is independent of the brushes, and is formed by the combs
and terminals.

Fig. 10.

The machine is self-exciting under all conditions of atmosphere,
owing probably to each plate being influenced by and influencing in
turn its neighbor, hence there is the minimum surface for leakage.
When excited, the direction of the current never changes; this
circumstance is due, probably, to the circuit of the metallic
sectors and the make and break contacts always being closed, while
the combs and the external circuit are supplemental, and for
external use only. The quantity of electricity is very large and
the potential high. When suitably arranged, the length of spark
produced is equal to nearly the radius of the disk. I have made
them from 2 in. to 7 ft. in diameter, with equally satisfactory
results. The diagram, Fig. 9, shows the distribution of the
electricity upon the plate surfaces when the machine is fully
excited. The inner circle of signs corresponds with the electricity
upon the front surface of the disk. The two circles of signs
between the two black rings refer to the electricity between the
disks, while the outer circle of signs corresponds with the
electricity upon the outer surface of the back disk. The diagram is
the result of experiments which I cannot very well repeat here this
evening, but in support of the distribution shown on the diagram, I
will show you two disks at work made of a flexible material, which
when driven in one direction close together at the top and the
bottom, while in the horizontal diameter they are repelled. When
driven in the reverse direction, the opposite action takes
place.

I have also experimented with the cylindrical form of the
machine (see Fig. 10). The first of these I made in 1882, and it is
before you. The cylinder gives inferior results to the simple
disks, and is more complicated to adjust. You notice I neither use
nor recommend vulcanite, and it is perhaps well to caution my
hearers against the use of that material for the purpose, for it
warps with age, and when left in the daylight it changes and
becomes useless.

Fig. 13.

Fig. 14.

I have now only to speak of the larger machines. They are in all
respects made up with the same plates, sectors, and brushes as were
used by me in the first experimental machines, but for convenience
sake they are fitted in numbers within a glass case. One machine
has eight plates of 2 ft. 4 in. diameter; it has been in the
possession of the Institution for about three years. A second,
which has been made for this lecture, has twelve disks, each 2 ft.
6 in. in diameter. The length of spark from it is 13⁵/₈ in. (see
Fig. 12). During the construction of the machine every care was
taken to avoid electrical excitement in any of its parts, and after
its completion several friends were present to witness the fitting
of the brushes and the first start. When all was ready the
terminals were connected to an electroscope, and the handle was
moved so slowly that it occupied thirty seconds in moving one-half
revolution, and at that point violent excitement appeared.

The machine has now been standing with its handle secured for
about eight hours. No excitement is apparent, but still it may not
be absolutely inert. Of this each one present must judge, but I
will connect it with this electroscope (Figs. 13 and 14), and then
move the handle slowly, so that you may see when the excitement
commences and judge of its absolutely reliable behavior as an
instrument for public demonstration. I may say that I have never,
under any condition, found this type of machine to fail in its
performance.

I now propose to show you the beautiful appearances of the
discharge, and then, in order that you may judge of the relative
capabilities of each of these three machines, we will work them all
at the same time.

The large frictional machine which is in use for this comparison
is so well known by you that a better standard could not be
desired.

In conclusion, I may be permitted to say that it is fortunate I
had not read the opinions of Sir William Thomson and Professor
Holtz, as quoted in the earlier part of my lecture, previous to my
own practical experiments. For had I read such opinions from such
authorities, I should probably have accepted them without putting
them to practical test. As the matter stands, I have done those
things which they said I ought not to have done, and I have left
undone those which they said I ought to have done, and by so doing
I think you must freely admit that I have produced an electric
generating machine of great power, and have placed in the hands of
the physicist, for the purposes of public demonstration or original
research, an instrument more reliable than anything hitherto
produced.

Violet Copying Ink.—Dissolve 40
parts of extract of logwood, 5 of oxalic acid and 30 parts of
sulphate of aluminium, without heat, in 800 parts of distilled
water and 10 parts of glycerine; let stand twenty-four hours, then
add a solution of 5 parts of bichromate of potassium in 100 parts
of distilled water, and again set aside for twenty-four hours. Now
raise the mixture once to boiling in a bright copper boiler, mix
with it, while hot, 50 parts of wood vinegar, and when cold put
into bottles. After a fortnight decant it from the sediment. In
thin layers this ink is reddish violet; it writes dark violet and
furnishes bluish violet copies.

SIBLEY COLLEGE LECTURES.—1887-88.

BY THE CORNELL UNIVERSITY NON-RESIDENT LECTURERS IN MECHANICAL
ENGINEERING.

The Evolution of the Modern
Mill.¹

By C. J. H. Woodbury, Boston,
Mass.

The great factories of the textile industries in this country
are fashioned after methods peculiarly adapted to the purposes for
which they are designed, particularly as regards the most
convenient placing of machinery, the distribution of power, the
relation of the several processes to each other in the natural
sequence of manufacture, and the arrangement of windows securing
the most favorable lighting. The floors and roofs embody the most
economical distribution of material, and the walls furnish examples
of well known forms of masonry originating with this class of
buildings.

These features of construction have not been produced by a
stroke of genius on the part of any one man. There has been no
Michael Angelo, no Sir Christopher Wren, whose epitaph bids the
reader to look around for a monument; but the whole has been a
matter of slow, steady growth, advancing by hair’s breadth; and, as
the result of continual efforts to adapt means to ends, an
inorganic evolution has been effected, resulting in the survival of
the fittest, and literally pushing the weaker to the wall.

This advance in methods has, like all inventions, resulted in
the impairment of invested capital. There are hundreds of mill
buildings, the wonder of their day, now used for storage because
they cannot be employed to sufficient advantage in manufacturing
purposes to compete with the facilities furnished by mills of later
design. Thus their owners have been compelled to erect new
buildings, and, as far as the original purpose of manufacturing is
concerned, to abandon their old mills.

In the case of a certain cotton mill built about thirty years
ago, and used for the manufacture of colored goods of fancy weave,
the owners added to the plant by constructing a one story mill,
which proved to be peculiarly adapted to this kind of manufacture,
by reason of added stability, better light, and increased
facilities for transferring the stock in process of manufacture;
and they soon learned not only that the old mill could not compete
with the new one, but that they could not afford to run it at any
price; the annual saving in the cost of gas, as measured by the
identical meter used to measure the supply to the old mill, being
six per cent. on the cost of the new mill.

In another instance, one of two cordage mills burned, and a new
mill of one story construction was erected in its place. The
advantage of manufacture therein was so great that the owners of
the property changed the remaining old mill into a storehouse; and
now, as they wish to increase their business, it is to be torn down
as a cumberer of the ground, to make room for a building of similar
construction to the new mill.

It is true that such instances pertain more particularly to
industries and lines of manufacture where competition is close and
conditions are exacting. Still they apply in a greater or less
degree to nearly every industrial process in which a considerable
portion of the expense of manufacture consists in the application
of organized labor to machines of a high degree of perfection.

These changes have been solely due to the differences in the
conditions imposed by improvement in the methods of manufacture.
The early mills of this country were driven by water power, and
situated where that could be developed in the easiest manner. They
were therefore placed in the narrow valleys of rapid watercourses.
The method of applying water power in that day being strictly
limited to placing the overshot or breast wheel in the race leading
from the canal to the river, the mill was necessarily placed on a
narrow strip of land between these two bodies of water, with the
race-way running under the mill.

To meet these conditions of location, which was limited to this
strip of land, the mill must be narrow and short, and the requisite
floor area must be obtained by adding to the number of stories. It
was essential that the roof of such a mill should be strong and
well braced in order to sustain the excessive stress brought to
bear upon it. The old factory roof was a curious structure, with
eaves springing out of the edge of hollow cornices, the roof rising
sharply until about six feet above the attic floor, with an upright
course of about three feet, filled with sashes reaching to a second
roof, which, at a more moderate pitch than the first slope, trended
to the ridge.

The attic was reduced to an approximately square room, by
placing sheathing between the columns underneath the sashes, and
ceiling underneath the collar beams above; thus forming a cock-loft
above and concealed spaces at the sides which diminished the
practically available floor space in the attic. This cock-loft and
these concealed spaces became receptacles for rubbish and harbors
for vermin, both of which were frequent causes of fire.

The floors of such a mill were similar in their arrangement to
those of a dwelling. Joists connecting the beams supported the
floor; and the under side was covered over by sheathing or lath and
plaster, thus forming, as in the case of the roof, hollow spaces
which were a source of danger. This method caused at the same time
an extravagant distribution of material, by the prodigal use of
lumber and the unnecessary thickness of such floors, and entailed
an excessive amount of masonry in the walls.

Mills built after this manner were frequently in odd dimensions;
and the machinery was necessarily placed in diversified
arrangement, calling forth a similar degree of wasted skill as that
used in making a Chinese puzzle conform to its given boundaries.
Their area depended upon the topography of the site, and their
height upon the owner’s pocket book. There was in Massachusetts a
mill with ten floors, built on land worth at that time ten cents or
less per square foot, which has been torn down and a new mill
rebuilt in its place, because, since the advent of modern mills, it
has failed every owner by reason of the excessive expenditure
necessary for the distribution of power, for supervision, and for
the transfer of stock in process, in comparison with the mills of
their competitors, built with greater ground area and less number
of stories.

With the advent of the steam engine as prime mover in mills, and
the introduction of the turbine wheel with its trunk, affording
greater facilities in the application of water power, the character
of these buildings changed very materially, though still retaining
many of their old features. One of the first of these changes may
be noticed in the consideration which millwrights gave to the
problem of fixing upon the dimensions of a mill so as to arrange
the machinery in the most convenient manner. Although the floors
were still hollow, there was a better distribution of material, the
joists being deeper, of longer span, and resting upon the beams,
thus avoiding the pernicious method of wasting lumber, and guarding
against fracture by tenoning joists into the upper side of
beams.

But this secondary type of mills was not honest in the matter of
design. The influence of architects who attempted effects not
accordant with or subservient to the practical use of the property
is apparent in such mills. The most frequent of these wooden
efforts at classic architecture was the common practice of
representing a diminutive Grecian temple surrounding a factory bell
perched in mid air. There were also windows with Romanesque arches
copied from churches, and Mansard roofs, exiled from their true
function of decorating the home, covering a factory without an
answering line anywhere on its flat walls.

I do not mean to criticise any of these elements of design in
their proper place and environment; but utility is the fundamental
element in design, and should be especially noticeable in a
building constructed for industrial purposes, and used solely as a
source of commercial profit in such applications. Its lines
therefore fulfill their true function in design in such measure as
they suggest stability and convenience; and this can be obtained in
such structures without the adoption of bad proportions offensive
to the taste. In fact, certain decorative effects have been made
with good results; but these have been wholly subordinate to the
fundamental idea of utility.

The endurance with which brick will withstand frost and fires,
and the disintegrating forces of nature, in addition to its
resistance to crushing and the facility of construction, constitute
very important reasons for its value for building purposes. But the
use of this has been too often limited to plain brick in plain
walls, whose monotony portrayed no artistic effect beyond that
furnished by a few geometrical designs of the most primitive form
of ornament, and falling far short of what the practice of recent
years has shown to be possible with this material.

Additions of cast iron serve as ornaments only in the
phraseology of trade catalogues; and the mixture of stone with
brick shows results in flaring contrasts, producing harsh
dissonance in the effect. The facades of such buildings show that
this is brick, this is stone, or this is cast iron; but they always
fail to impress the beholder with the idea of harmonious design.
The use of finer varieties of clay in terra cotta figures laid
among the brickwork furnishes a field of architectural design
hardly appreciated. The heavy mass of brick, divided by regular
lines of demarkation, serves as the groundwork of such
ornamentation, while the suitable introduction in the proper places
of the same material in terra cotta imparts the most appropriate
elements of beauty in design; for clay in both forms shows alike
its capacity for utility and decoration. The absorption of light by
both forms of this material abates reflection, and renders its
proportions more clearly visible than any other substance used in
building construction.

The modern mill has been evolved out of the various exacting
conditions developed in the effort to reduce the cost of production
to the lowest terms. These conditions comprise in a great measure
questions of stability, repairs, insurance, distribution of power,
and arrangement of machinery.

In presenting to your attention some of the salient features of
modern mill construction, I do not assume to offer a general
treatise upon the subject; but propose to confine myself to a
consideration of some topics which may not have been brought to
your notice, as they are still largely matters of personal
experience which have not yet found their way into the books on the
subject. Much of this, especially the drawings thrown on the
screen, is obtained from the experience of the manufacturers’
mutual insurance companies, with which I am connected. By way of
explanation, I will say that these companies confine their work to
writing upon industrial property; and there is not a mechanical
process, or method of building, or use of raw material, which does
not have its relation to the question of hazard by fire, by reason
of the elements of relative danger which it embodies.

It is indeed fortunate that it has been found by experience that
those methods of building which are most desirable for the
underwriter are also equally advantageous for the manufacturer.
There is no pretense made at demands to compass the erection of
fireproof buildings. In fact, as I have once remarked, a fireproof
mill is commercially impossible, whatever effort may be made to
overcome the constructive difficulties in the way of erecting and
operating a mill which shall be all that the name implies. The
present practice is to build a mill of slow burning
construction.

FOUNDATIONS.

In considering the elements of such buildings, I wish to devote
a few words to the question of foundations, because in the
excessive loads imposed by this class of buildings, and in the
frequent necessity of constructing them upon sites where alluvial
drift or quicksands form compressible foundations, there is
afforded an opportunity for the widest range of engineering skill
in dealing with the problem. In such instances, a settling of the
building must be foreseen and provided for, in order that it may be
uniform under the whole structure. This is generally accomplished
by means of independent foundations under the various points of
pressure, arranged so as to give a uniform intensity of pressure
upon all parts of the foundation. It is considered important to
limit the load upon such foundations to two tons a square foot,
although loads frequently exceed this amount.

There is a large building in New York City which has recently
been reconstructed, and the foundations rearranged, where the load
reached to the enormous amount of six to ten tons per square foot.
It was a frequent occurrence in the class of high mills spoken of
to impose loads of so much greater intensity upon the wall
foundation than upon the piers under the columns of the mill, that
the floors became much lower at the walls than at the middle.

The stone for such foundations should be laid in cement rather
than in mortar, not merely because cement offers so much greater
resistance to crushing, but because its setting is due to chemical
changes occurring simultaneously throughout the mass. The hardening
of mortar, on the other hand, is due to the drying out of the water
mechanically contained with it, and its final setting is caused by
the action of the carbonic acid gas in the air.

Although quicksands are never to be desired, yet they will
sustain heavy loads if suitably confined. When inclined rock strata
are met with, all horizontal components of stress should be removed
by cutting steps so that the foundation stones shall lie upon
horizontal beds.

Foundations are frequently impaired by the slow, insidious
action of springs or of water percolating from the canal which
supplies the water power for the mill; and the proper diversion of
such streams should be carefully provided for.

In the question of foundations, there is much of a general
nature which is applicable to all structures; but, at the same
time, each case requires independent consideration of the
circumstances involved.

WALLS.

In addition to what has been said, there is but little for me to
offer on the subject of walls beyond the general question of
stability. In mill construction, walls of uniform thickness have
been displaced by pilastered walls, about sixteen inches thick at
the upper story, and increasing four inches in thickness with each
story below.

The remainder of the walls is from four to six inches less in
thickness than at the pilasters. Frequently the outside dimensions
of these pilasters are somewhat increased, giving greater stability
and artistic effect. By leaving hollow flues within them, and using
these flues as conductors for heated air which may be forced in by
a blower, such pilasters afford a means for the most efficient
method of warming the building.

Consideration must be given to the contraction of brick masonry,
especially when an extension or addition is to be made to an older
building. This shrinkage amounts to about three-sixteenths of an
inch to the rod, an item which is of considerable importance in the
floors of high buildings, where the aggregate difference is very
appreciable. Some degree of annoyance is caused by neglect to
consider this element of shrinkage in reference to the window and
door frames, which should have a slight space above them allowing
for such contraction. This contraction is often the source of
serious trouble in brick buildings with stone faces, the shrinkage
of the brick imposing excessive stress on the stone. Instances of
this are quite frequent, especially in large public buildings,
notably the capitol at Hartford and the public building at
Philadelphia, where the shivering of the joints of the stone work
gave undue alarm, on the general assumption that it indicated a
dangerous structural weakness. The difficulty has, I believe, been
entirely remedied in both cases.

The limit of good practice on loads upon brickwork is eight to
ten tons per square foot, although it is true that these loads are
largely exceeded at times. It is not to be shown, however, that the
limits of safety in regard to desirable construction should be
confined to the use of masonry for any low buildings. Structures
which may be said to be equal to those of brickwork, as far as
commercial risk is concerned, can be built wholly or in part of
wood so as to conform to all practical conditions of safety. This
statement does not apply except to low buildings of one or possibly
two stories in height, where the timber cannot be subjected to the
intense blast of flame occurring when a high building is on
fire.

Mr. George H. Corliss, the eminent engine builder, of
Providence, first built a one-story machine shop, with brick walls
extending only to the base of the windows, above this the windows
being very close together, with solid timber construction between
them.

Another method is to place upright posts reaching from the sill
to the roof timbers, and to lay three-inch plank on the outside of
such posts up to the line of the windows. A sheathing on the
outside plank between the timbers is laid vertically and fastened
to horizontal furring strips. In some instances a small amount of
mortar is placed over each of the furring strips. The reason for
this arrangement is to prevent the formation of vertical flues,
which are such a potent factor in the extension of fires.

WINDOWS.

Light is often limited or misapplied on account of faulty
position or size of windows. The use of pilastered walls permits
the introduction of larger windows, which are in most instances
virtually double windows, the two pairs of sashes being set in one
frame separated by a mullion. A more recent arrangement, widely
adopted in English practice, is to place a swinging sash at the top
of the window, which can be opened, when necessary, to assist in
the ventilation, while the main sashes of the window are
permanently fixed.

Rough plate glass is used in such windows, because it gives a
softer and more diffused light, which is preferred to that from
ordinary clear glass. White glass may be rendered translucent by a
coat of white zinc and turpentine.

The top of a window should be as near the ceiling as
practicable, because light entering the upper portion of a room
illuminates it more evenly, and with less sharply marked shadows,
than where the windows are lower down.

The walls below the windows should be sloped, in order that
there may be no opportunity to use them as a resting place for
material which should be placed elsewhere.

FIRE WALLS.

Brick division walls should be built so as to constitute a fire
wall wherever it is practicable to do so. Such walls should project
at least three feet above the roof, and should be capped by stone,
terra cotta, or sheet metal. They must form a complete cut-off of
all combustible material, especially at the cornices.

FIRE DOORS.

All openings in such walls must be provided with such fireproof
doors as will prove reliable in time of need. Experience with iron
doors of various forms of construction show that they have been
utterly unreliable in resisting the heat of even a small fire. They
will warp and buckle so as to open the passageway and allow the
fire to pass through the doorway into the next room.

A door made of wood, completely enveloped by sheets of tinned
iron, and strongly fastened to the wall, has proved to resist fire
better than any door which can be applied to general use. I have
seen such doors in division walls where they had successfully
resisted the flame which destroyed four stories of a building
filled with combustible material, without imposing any injury upon
the door except the removal of the tin on the sheet iron; and the
doors were kept in further service without any repairs other than a
coat of paint.

The reason for this resistance to fire is that the wood, being a
poor conductor of heat, will not warp and buckle under heat, and
cannot burn for lack of air to support combustion. A removal of the
sheet metal on such a door after a fire in a mill shows that the
surface of the wood is carbonized, not burned, reduced to charcoal,
but not to ashes.

Many fire doors are constructed and hung in such a manner that
it is doubtful whether they could withstand a fire serious enough
to require their services.

The door should be made of two thicknesses of matched pine
boards of well dried stock, and thoroughly fastened with clinched
nails. It should be covered with heavy tin, secured by hanging
strips, and the sheets lock-jointed to each other, with the edge
sheets wrapping around, so that no seam will be left on the
edge.

Sliding doors are preferable to swinging doors for many reasons,
especially because they cannot be interfered with by objects on the
floor. But, if swinging doors are used, care should be taken that
the hinges and latches are very strong, and securely fastened
directly to the walls, and not to furring or anything in turn
attached to the walls. The portion of the fixtures attached to the
doors must be fastened by carriage bolts, and not by wood
screws.

Sliding on trucks is the preferable method of hanging sliding
doors, inclined two and one half inches to the foot, and bolted to
the wall. The trucks should be heavy “barn door hangers,” bolted to
the door; and a grooved door jamb, of wood, covered with tin
similar to the door, should receive it when shut. A step of wood
will hold the door against the wall when closed. A threshold in the
doorway retards fire from passing under the door, and also prevents
the flow of water from one room to another.

These doors are usually placed in pairs, and sometimes an
automatic sprinkler is placed between them.

Fire doors should always be closed at night. In some well
ordered establishments there is a printed notice over each door
directing the night watchmen to close such doors after them. In a
storage warehouse in Boston, the fire doors are connected with the
watchman’s electric clock system, so that all openings of fire
doors are matters of record on the dial sheet.

Fire doors should certainly be closed at times of fire; yet,
that such doors are open at night fires, or left open by fleeing
help at day fires, is an old story with underwriters. A simple
automatic device can be used to shut such doors. It consists of two
round pieces of wood with a scarfed joint held by a ferrule,
forming a strut which is placed on two pins, keeping the door open,
as other sticks have long since served like purposes.

The peculiarity of this arrangement is that the ferrule is not
homogeneous, but is made up of four segments of brass soldered
together with the alloy fusible at 163 degrees Fahr., which is
widely known for its use in automatic sprinklers. When the solder
yields, the rod cripples, and the door rolls down the inclined rail
and shuts. At any time the door can be closed by removing one end
of the rod from one of the pins and allowing it to hang from the
other pin.

MILL TOWERS.

Because of economic reasons for preserving the space within the
walls of the mill so that it may be to the greatest extent
available for the best arrangement of machinery, the stairways
should be placed outside of the building. Such stairways should not
be spiral stairways, but should be made in short straight runs with
square landings, because in the spiral stairway the portion of the
stairs near the center is of so much steeper pitch that it renders
them dangerous when the help are crowding out of the mill.

The wear of stairs from the tread of many feet presents a
difficult problem. A very common practice consists in covering each
tread with a thin piece of cast iron marked with diagonal scores,
and generally showing the name of the mill. These treads wear out
in the course of time, but for this use they answer very well,
although somewhat slippery.

A wood tread gives a more secure foothold upon the stairway; and
in some instances stairs have been protected by covering the treads
with boards of hard wood, containing grooves about three-eighths of
an inch deep, and of similar width, with a space of half an inch
between them. These boards are grooved on both sides and placed on
the stairs. After the front edge is worn, they are turned around so
as to present the other edge to the front, and, in course of time,
turned from the exposed side to do service in two positions on the
other side. In this manner these tread covers are exposed to wear
in four different positions.

Mill towers, besides containing the stairways, also serve other
purposes, as for cloak rooms for the help. They often contain a
part of the fire protective apparatus, carrying standpipes with
hydrants at each floor. For this use they are easily available, and
furnish a line of retreat in case a fire spreads to an extent
beyond the ability of the apparatus to cope with it. These towers
also furnish an excellent foundation for the elevated tank
necessary for the supply of water for the fire apparatus in places
unprovided with an elevated reservoir.

In view of the terrible and deplorable accidents which have
occurred by reason of lack of proper stairway facilities at panics
caused in time of fire, I would repeat the words of the late Amos
D. Lockwood, the most eminent mill engineer which this country has
yet produced, when he said to the New England Cotton Manufacturers’
Association, “You have no moral right to build a mill employing a
large number of help, with only one tower containing the stairways
for exit.”

The statute laws of several of the States require fire escapes;
but it is a matter of fact that they are rarely used, because
people are not often cool enough to avail themselves of that
opportunity of escape. I know of one instance where a number of
girls jumped out of a fourth story window, because they did not
think of the stairways, and did not dare to use the fire escape. In
that instance, none of the group referred to tried to go down the
stairs, which did furnish a perfectly safe means of exit to a
number of others.

Most of the fire escapes are put up so as to conform to the
letter of the law; and in such manner that no one but a sailor or
an acrobat would be likely to trust himself to them. In crowded
city buildings, and in other places where the ordinary means of
escape are not in duplicate, it is essential that fire escapes
should be provided; but it is a great deal better to make a mill
building so that they shall not be necessary as a matter of fact,
even if they are put up to conform to the requirements of statute
law.

REAR TOWERS.

In addition to stairways, towers are placed at the rear of the
mill, for the purpose of accommodating the elevators and sanitary
arrangements. It is not desirable that elevators should be boxed or
surrounded with anything that would result in the construction of a
flue; but it is preferable that they pass directly through the
floors, with the openings protected by automatic hatchways which
close whenever the elevator car is absent. In the washroom, etc.,
in these towers, it is desirable to protect the wood floors by
means of a thin layer of asphalt.

BASEMENT FLOORS.

There are difficulties connected with the floors on or near the
ground, by reason of the dry rot incident to such places. Dry rot
consists in the development of fungus growth from spores existing
in the wood, and waiting only the proper conditions for their
germination. The best condition for this germination is the
exposure to a slight degree of warmth and dampness. There have been
many methods of applying antiseptic processes for the preservation
of wood; but, irrespective of their varying degrees of merit, they
have not come into general use on account of their cost, odor, and
solubility in water.

It is necessary that wood should be freely exposed to
circulation of air, in order to preserve it under the ordinary
conditions met with in buildings. Whenever wood is sealed up in any
way by paint or varnish, unless absolutely seasoned, and in a
condition not found in heavy merchantable timber, dry rot is almost
sure to ensue. Whitewash is better.

There has recently been an instance of a very large building in
New York proving unsafe by reason of the dry rot generated in
timbers which have been completely sealed up by application of
plaster of Paris outside of the wire lath and plaster originally
adopted as a protection against fire. Wire lath and plaster is one
of the best methods of protecting timber against fire; and, if the
outside is not sealed by a plaster of stucco or some other
impermeable substance, the mortar will afford sufficient facilities
for ventilation to prevent the deposition of moisture, which will
in turn generate dry rot.

Where beams pass into walls, ventilation should be assured by
placing a board each side of the beam while the walls are being
built up, and afterward withdrawing it. In the form of hollow walls
referred to, it is a common practice to run the end of the beam
into the flue thus formed, in order to secure ventilation.

I am well acquainted with a large mill property, one building of
which was erected a short time before the failure of the
corporation, which resulted in the whole plant remaining idle
several years. After the lapse of about five years this
establishment was again put into operation; but before the new mill
could be safely filled with machinery, it was necessary to remove
all the beams which entered walls and to substitute for them new
ones, because the ends were so thoroughly rotted that it would have
been dangerous to impose any further loads upon the floors. When
floors are within a few feet of the ground, unless the site be
remarkably dry, it is essential to provide for a circulation of
air, which can be done very feasibly in a textile mill by laying
drain pipe through the upper part of the underpinning, forming a
number of holes leading into this space, and then making a flue
from this space to the picker room or any other place requiring a
large amount of air. The fans of the picker room, drawing their
supply from underneath the building, produce a circulation of air
which keeps the timber in good condition.

It is supposed by some that there is a difference in the quality
of timber according to the season in which it is felled, preference
being given to winter timber, on account of the greater amount of
potash and phosphoric acid which it is said to contain at that
time. In some parts of Europe it is a custom to specify that the
lumber should have been made from rafted timber, on account of the
action of the water in killing certain species of germs. Whatever
may be the merits of either of these two theories, the commercial
lumber of the northern part of this country is generally felled in
winter and afterward rafted.

The action of lime in the preservation of wood has always been
attended with the most excellent results; although not suited to
places subject to the action of water, which dissolves the lime,
leaving the timber practically in its original condition. The
preservative action of lime upon wood is readily shown by the
admirable condition in which laths are always found. I doubt if any
one ever found a decayed lath in connection with plaster.

As an example of the action of lime as a preservative of lumber.
I can cite an instance of a mill in New Hampshire where the
basement floor was placed in 1856, the ledge in the cellar having
been blasted out for the purpose. The rock was very seamy, and
abounded in water issuing from springs or percolating from the
canal supplying water to the mill. The rock was blasted away to a
grade two feet below the floor, and most of the space filled up
again by replacing the small pieces of stone, so arranged as to
form blind drains for the removal of any water which might find its
way under the floor.

Toward the top of this filling, finer stones were used,
then
about three inches of gravel, which was covered with two inches of
sand and lime. Two years ago I was at this mill when some
alterations requiring the removal of the floor were in progress,
and found that the lumber was still in good, sound condition,
except for a superficial decay on the under side of the floor
plank.

But there are frequent instances where it is necessary to place
the floor directly upon the earth, without any space or loose
filling underneath it, in order to save room, or to secure a firm
support for machinery. By way of information upon what has actually
been accomplished in this direction, I will cite instances of three
floors in such positions, all of which have to my knowledge
fulfilled the purpose for which they were designed.

The first instance is that of a basement floor laid twenty-one
years ago, a portion of which was made by excavating one foot below
the floor, six inches of coarse stone being filled in, then five
inches of coal tar concrete made up with coarse gravel, and finally
about one inch of fine gravel concrete. Before the concrete was
laid, heavy stakes were driven through the floor about three feet
apart, to which the floor timbers were nailed and leveled up. The
concrete was then filled in upon the floor timbers, and thoroughly
tamped and rolled out to the level of the top of the floor timbers.
The under side of the floor timbers was covered with hot coal
tar.

This floor is still in good condition, and has not needed
repairs caused by the decay of the timber. Another portion of the
floor laid at the same time and in the same manner, with the
exception that cement concrete was used in the place of the coal
tar, was entirely rotted out in ten years.

Another floor was made in quite a similar manner. All soil and
loam was removed from the interior of the building; the whole
surface was brought up to the grade with a puddle of gravel and
ashes; stakes two and a half by four inches, and thirty inches in
length, were driven down; and nailing strips were secured to them.
Over this puddled surface a coat of concrete eight inches thick was
laid, the top being flush with the upper surface of the nailing
strips. This concrete was made of pebbles about two inches in
diameter, well coated with coal tar, and laid in place when hot. It
was then packed together by being tamped and rolled, and a thin
covering of the tarred sand placed upon the top, forming a smooth,
hard surface. The first floor consisted of two inches of matched
spruce, grooved on both sides, and fitted with hard pine splines,
five-eighths by one and one-fourth inches. On the top of this a
hard pine 1¼ inch floor was laid over a course of building
paper.

Another method, which is certainly more novel than either of the
others, consists in supporting a floor upon a bed of resin. The
underlying earth was removed, and replaced with spent moulding
sand, leaving trenches for the floor timbers, which were placed
upon bricks laid without mortar. Melted resin was poured into the
space alongside and underneath the timbers. The floor planks were
then laid upon the timbers, the tops of which were about half an
inch above the level of the sand. Holes were bored into the floor
plank about four feet apart, and melted resin then poured into the
holes, so as to interpose a layer of resin underneath the floor
plank and beams. Upon this floor a top floor of hard wood was laid
in the usual manner. This floor has been used for a number of years
to support a large quantity of heavy machine tools, principally
planers, without yielding or depreciation due to decay, and has
proved to be most satisfactory.

In some instances asphaltum or coal tar concrete floors are not
covered with wood, although it is much more agreeable for the help
to stand upon wooden floors. It should be remembered that all these
compounds are readily softened by means of oil, and they should be
protected from oil by a coat of paint when not covered with wood;
the preferable method being to first apply a priming containing
very little oil, or a coat of shellac, and follow with some paint
mixed up with boiled linseed oil.

(To be continued.)

THE MECHANICAL EQUIVALENT OF HEAT.

By De Volson Wood, Professor of
Engineering in Stevens Institute of Technology.

It is clearly intimated by Mr. Hanssen, in his determination of
the mechanical equivalent of heat, published in the Scientific American Supplement, No. 642, April 21,
1888, that his object is to determine the absolute value of
this constant. With his data he finds it to be 771.89 foot pounds.
But the determination by direct experiment gives a larger value.
Thus, the most reliable experiments—those of Joule and
Rowland—give values exceeding by several units that found by
Hanssen. A committee of the British Association, appointed for this
purpose, reported in 1876 that sixty of the most reliable of
Joule’s experiments gave the mean value 774.1. The experiments were
made with water at a temperature of about 60° F., according to
the mercurial thermometer, and reduced to its value at the
temperature of melting ice, according to the formula given by
Regnault for the variation of the specific heat of water at varying
temperature under the constant pressure of one atmosphere.
According to this formula the specific heat of water increases with
the temperature above the melting point of ice, so that the
equivalent would be somewhat less at 32° F. than at 60° F.
It will be found in Regnault’s Relation des Experiences that
he experimented on water at high temperatures, but more recently
Professor Rowland has found that the specific heat of water is
greater at 40° F. than at 60° F., thus reversing
between these limits the law given by Regnault; the increase, as
given by the most probable values, being, roughly, about ¹/₂₅₀ of
its value at 60° F. The proper correction due to this cause
would make the equivalent over 777 foot pounds, instead of 774.1.
Professor Rowland’s experiments, when reduced to the same
thermometer, same temperature, and same latitude as Joule’s, agreed
very nearly with those of the latter, being about ¹/₁₀₀₀ part
larger; so that the chief difference in the ultimate values
consists in the reductions for temperature and latitude. The force
of gravity being less for the lower latitudes, the number
representing the mechanical equivalent will be greater for the
latter, since the unit pound mass must fall through a greater
number of feet to equal the same work; so that the equivalent will
be greater at Paris than at Manchester. Professor Rowland also
found that the degrees on the air thermometer from 40° F.
upward to above 60° F. exceeded those on the mercurial
thermometer throughout the corresponding range, and that from
40° to 41° the degree was between ¹/₁₅₀ and ¹/₂₀₀ of a
degree larger on the air thermometer than on the mercurial.
Although this fraction is too small to be observed by ordinary
means, yet, if it exists, it cannot be ignored if absolute values
are sought. Regnault employed the air thermometer in his
experiments, while Joule used the mercurial thermometer, and if
Joule’s value 774.1 be increased by ¹/₂₀₀ of itself in order to
reduce it from the equivalent of the degree on the mercurial
thermometer to that on the air thermometer, we get 778 foot pounds,
nearly. Rowland found from his experiments that when reduced to the
air thermometer and to the latitude of Baltimore, the equivalent
was nearly 783, subject to small residual errors.

Nearly all writers upon this subject—except
Rankine—have considered that the mechanical equivalent of
heat, in British units, was the energy necessary to raise the
temperature of one pound of water from 32° F. to 33° F.,
but Rankine defines it as the heat necessary to increase the
temperature of one pound of water one degree Fahrenheit from that
of maximum density, or from 39° F. to 40° F. For ordinary
practice it is immaterial which of these definitions is used, for
the errors resulting therefrom are much less than those resulting
from ordinary observations. But when the value is to be determined
by direct experiment at the standard temperature, Rankine’s limits
are much to be preferred; for it is so very difficult to determine
exact values by observation when the substance is near the state
bordering on a change of state of aggregation, as that of changing
from water to ice. Observations made at about 60° F. were
reduced by means of Regnault’s law for the specific heat of water,
as has been stated, which is expressed by the formula

in which t denotes the temperature according to the
Centigrade scale. According to this law, the mechanical equivalent
would not be 0.2 of a foot pound greater at 5° C. (41° F.)
than at 0° C. (32° F.); hence, if this law were correct, it
would make no practical difference whether the temperature were at
0° C. or 5° C. This law makes the computed value at
32° F. about 0.95 of a foot pound less than that determined by
experiment at 60° F.; whereas Rowland’s experiments make it
greater at 40° F. by more than four foot pounds, for the
air thermometer. In determining a fixed value to be used for
scientific purposes, it is necessary to fix the place, the
thermometer, and the particular degree on the thermometer. The
place may be known by its latitude if reduced to the level of the
sea. The air thermometer agrees most nearly with that of the
ideally perfect gas thermometer, while the mercurial thermometer
differs very much from it in some cases. Thus, Regnault found that
when the air thermometer indicated 630° F. above the melting
point of ice (or 662° F.), the mercurial thermometer indicated
651.9° above the same point (683.9° F.), a difference of
22° F. It is apparent that the air thermometer furnishes the
best standard. As for the particular degree on the scale to be used
for the standard, it is apparent, from the observations above made,
that the temperature corresponding to that at or near the maximum
density of water is more desirable than that at the melting point
of ice. The fact, also, that the specific heats at constant
pressure and at constant volume are the same at the point of
maximum density, as shown by theory, is an additional argument in
favor of selecting this point for the standard. It thus appears
that the solution of this problem, which appears simple and very
definite by Mr. Hanssen’s method, becomes intricate and, to a
limited degree, indeterminate when subjected to the refinements of
direct experiment. If the constants used by Hanssen are absolutely
correct, then his result must be unquestioned; but since physical
constants are subject to certain residual errors, one would as soon
think of finding the specific heat of air at constant volume, by
using the value of the mechanical equivalent as one of the
elements, and trusting the result, as he would to trust to the
computed value of the mechanical equivalent without subjecting it
to the test of a direct experiment. We will, therefore, examine the
constants used to see if they are the exact values of the
quantities they represent.

He says they are universally accepted as correct; and this may
be true, when used for general purposes, and yet not be
scientifically exact. He uses 0.2377 as the specific heat of air.
This is the value, to four decimals, found by Regnault. Thus,
Regnault gives for the mean value of the specific heat of air

And we know of no reason why one of these values should be used
rather than another, except that the mean of a large range of
temperatures may be more nearly correct than that of any other; and
if this reason determines our choice, the number 0.2375 would be
used instead of 0.2377. Although this difference is small, yet the
former value would have reduced his result about 0.7 of a foot
pound.

Again, he uses 0.1686 for the specific heat of air at constant
volume. The value of this constant has never been found to any
degree of accuracy by direct experiment, and we are still dependent
upon the method established by La Place and Poisson, according to
which the constant ratio of the specific heat of a gas at constant
pressure to that at constant volume is found by means of the
velocity of sound in the gas. The value of the ratio for air, as
found in the days of La Place, was 1.41, and we have 0.2377
÷ 1.41 = 0.1686, the value used by Clausius, Hanssen, and
many others. But this ratio is not definitely known. Rankine in his
later writings used 1.408, and Tait in a recent work gives 1.404,
while some experiments give less than 1.4, and others more than
1.41.

An error of one foot in a thousand in determining the velocity
of sound will affect the third decimal figure one or two units. A
small difference in the assumed weight of a cubic foot of air also
affects the result. M. Hanssen gives 0.080743 pound as the weight
at 32° F. under the pressure of one atmosphere; while Rankine
gives 0.080728 pound. In my own computations I use 1.406 as a more
probable value of the constant sought. This will give for the
specific heat of air at constant pressure

This is only 0.0003 of a unit greater than the value used by
Hanssen, but it would have given him nearly 775, instead of
771.89.

Again, he uses 491.4° F. for the absolute temperature of
melting ice. The exact value of this constant is unknown; but the
mean value as determined by Joule and Thomson, in their celebrated
experiments with porous plugs, was 492.66° F. This value would
slightly change his result. It will be seen from the above that a
small change in the constants used may affect by several units the
computed value of the mechanical equivalent. I have computed it,
using 1.406 for the ratio of the specific heat of air at constant
pressure to that at constant volume, 491.13° F. as the
temperature of melting ice above the zero of the air
thermometer, 26,214 feet for the height of a homogeneous
atmosphere, and 0.2375 for the specific heat of air, and I find, by
means of these constants, 778. If computed from the zero of the
absolute scale, 492.66° F., I find 777 to the nearest integer.
Recently I have used 778. If the value given by Rowland, about 783
according to the air thermometer at 39° F., should prove to be
correct, it seems probable that the constant 1.406 used above would
be reduced to about 1.403, or that the other constants must be
changed by a small amount. The height of the homogeneous atmosphere
used above, 26,214 feet, is the value used by Rankine as deduced
from Regnault’s figures, and only one foot less than the value used
by Sir William Thomson; but the figures used by Mr. Hanssen give
26,210½ feet.

The method above called Hanssen’s is really that of Dr. Mayer
(the German professor), who in 1842 used it for determining the
mechanical equivalent; but on account of erroneous data, the value
found by him was much too small.

ECONOMY TRIALS OF A NON-CONDENSING STEAM
ENGINE—SIMPLE, COMPOUND, AND TRIPLE.¹

By Mr. P. W. Willans, M.I.C.E.

The author described a series of economy trials, non-condensing,
made with one of his central valve triple expansion engines, with
one crank, having three cylinders in line. By removing one or both
of the upper pistons, the engine could be easily changed into a
compound or into a simple engine at pleasure. Distinct groups of
trials were thus carried out under conditions very favorable to a
satisfactory comparison of results.

No jackets were used, and no addition had, therefore, to be made
to the figures given for feed water consumption on that account.
Most of the trials were conducted by the author, but check trials
were made by Mr. MacFarlane Gray, Prof. Kennedy, Mr. Druitt Halpin,
Professor Unwin, and Mr. Wilson Hartnell. The work theoretically
due from a given quantity of steam at given pressure, exhausting
into the atmosphere, was first considered.

By a formula deduced from the θ φ diagram of Mr.
MacFarlane Gray, which agreed in results with the less simple
formulas of Rankine and Clausius, the pound weight of steam of
various pressures required theoretically per indicated horse power
were ascertained. (See annexed table.)

A description was then given of the main series of trials, all
at four hundred revolutions per minute, of the appliances used, and
of the means taken to insure accuracy. A few of the results were
embodied in the table. The missing quantity of feed water at cut
off, which, in the simple trials, rose from 11.7 per cent. at 40
lb. absolute pressure to nearly 30 per cent. at 110 lb. and at 90
lb. was 24.8 per cent., was at 90 lb. only 5 per cent. in the
compound trials. In the latter, at 160 lb., it increased to 17 per
cent., but, on repeating the trial with triple expansion, it fell
to 5.46 per cent. or to 4.43 per cent. in another trial not
included in the table.

On the other hand, from the greater loss in passages, etc., the
compound engine must always give a smaller diagram, considered with
reference to the steam present at cut-off, than a simple engine,
and a triple a smaller diagram than a compound engine.
Nevertheless, even at 80 lb. absolute pressure, the compound engine
had considerable advantage, not only from lessened initial
condensation, but from smaller loss from clearances, and from
reducing both the amount of leakage and the loss resulting from it.
These gains became more apparent with increasing wear. The greater
surface in a compound engine had not the injurious effect sometimes
attributed to it, and the author showed how much less the
theoretical diagram was reduced by the two small areas taken out of
it in a compound engine than by the single large area abstracted in
a simple engine. The trials completely confirmed the view that the
compound engine owed its superiority to reduced range of
temperature. At the unavoidably restricted pressures of the triple
trials, the losses due to the new set of passages, etc., almost
neutralized the saving in initial condensation, but with increased
pressure—say to 200 lb. absolute—there would evidently
be considerable economy. The figures of these trials showed that
the loss of pressure due to passages was far greater with high than
with low pressure steam, and that pipes and passages should be
proportioned with reference to the weight of steam passing, and not
for a particular velocity merely.

The author described a series of calorimetric tests upon a large
scale (usually with over two tons of water), the results of which
were stated to be very consistent. After comparing the dates of
initial condensation in cases where the density of steam, the area
of exposed surface, and the range of temperature were all
variables, with other cases (1) where the density was constant and
(2) where the surface was constant, the author concluded that, at
four hundred revolutions per minute, the amount of initial
condensation depended chiefly on the range of temperature in the
cylinder, and not upon the density of the steam or upon the extent
of surface, and that its cause was probably the alternate heating
and cooling of a small body of water retained in the cylinder. The
effect of water, intentionally introduced into the air cushion
cylinder, corroborated the author’s views, and he showed how small
a quantity of water retained in the cylinder would account for the
effects observed. At lower speeds surface might have more
influence. The favorable economical effect of high rotative speed,
per se, was very apparent.

In a trial with a compound engine, with 130 lb. absolute
pressure, the missing quantity at cut-off rose from 11.7 per cent.
at 405 revolutions to 29.66 per cent. at 130 revolutions, the
consumption of feed water increasing from 20.35 lb. to 23.67 lb.
This saving of 14 per cent. was due solely to increase of speed.
Similar trials had been made with a simple engine. In one simple
trial at slow speed the missing quantity rose to 44.5 per cent. of
the whole feed water.

The author compared a series of compound trials, at different
powers, with 130 lb. absolute pressure, and various ratios of
expansion, with a series giving approximately the same powers at a
constant ratio of expansion, but with varying pressures, being
practically a trial of automatic expansion against throttling.
Starting with 40 indicated horse power, 130 lb. absolute pressure,
four expansions, and a consumption of 20.75 lb. of water, the plan
of varying the expansion, as compared with throttling, showed a
gain of about 7 per cent. at 30 indicated horse power, but of a
very small percentage when below half power. If the engine had an
ordinary slide valve, the greater friction, added to irregular
motion, would probably neutralize the saving, while if the engine
were one in which initial condensation assumed more usual
proportions, the gain would be probably on the side of variable
pressure. Even as it was, the diagrams showed that the missing
quantity became enormously large as the expansion increased.
Judging only by the feed water accounted for by the indicator, the
automatic engine appeared greatly the more economical, but actual
measurement of the feed water disproved this. The position of the
automatic engine was, however, relatively more favorable when
simple than when compound.

In conclusion, the author referred to a trial with a condensing
engine, at 170 lb. absolute pressure, in which the feed water used
was 15.1 lb., a result evidently capable of further improvement,
and to an efficiency trial of a combined central valve engine and
Siemens’ dynamo, made for the Admiralty, at various powers. At the
highest power the ratio of external electrical horse power to
indicated horse power in the engine was 82.3 per cent. Taking the
thermo-dynamic efficiency of the engine at 80 per cent., that of
the combined apparatus would be nearly 66 per cent.

RAILWAY BRIDGE AT LACHINE.

The subject of our large illustration this week is a large steel
bridge carrying the Central Pacific Railway over the St. Lawrence
River at Lachine, near Montreal. The main features of this really
magnificent structure are the two great channel spans, each 408
feet long. It will be noticed that the design combines, in a very
ingenious manner, an upper and a lower deck structure, the railway
track being laid on the top of the girders forming the side spans,
and on the lower flanges of the channel spans, which are crossed by
continuous girders, 75 feet deep, over the central pier, and
supported by brackets as shown. The upper of our two engravings
shows the method of constructing the principal spans, which were
built outward from the side piers, while the work on the center
pier was extended on each side to meet. It was built at the works
of the Dominion Bridge Company, Montreal, from the design of Mr. C.
Shaler Smith, the well-known American bridge
engineer.—Engineering.

IMPROVED SCREW PROPELLER.

While the last few years have seen great advances made in the
designs of steamships and of their engines, little or nothing has
been done in the way of improving the screw propeller. As a general
rule it would appear to be taken for granted that no radical
improvement could be made in the form of the propeller, although
various metals have been introduced in its manufacture with the
view of increasing its efficiency. For sea-going steamers, however,
the shape remains the same, the variation chiefly relating to the
number of blades employed. A striking departure from ordinary
practice, however, has of late been made by Mr. B. Dickinson, who
has invented a screw propeller which, on practical trial, has given
an efficiency far in advance of the ordinary screw. This new
propeller we illustrate here in Figs. C and D, while Fig. A shows
an ordinary propeller. The Dickinson propeller illustrated has six
blades, giving a surface of 30 square feet; it is right handed, and
has pitch of 15 ft. and a diameter of 10 ft. 6 in. The ordinary
screw propeller shown at Fig. A is right handed and two bladed,
with a pitch at the boss of 13 ft. 6 in. and at the tip of 15 ft.
It has a diameter of 10 ft. 9 in. and 32 square ft. of surface. The
projected area looking forward is 22 square ft. and the projected
area looking athwartship 22.84 square feet. The most graphic way of
illustrating the principle of Mr. Dickinson’s propeller is to take
a two bladed propeller of the ordinary type as shown at Fig. A in
the annexed cuts, and divide into three sections as in Fig. B, then
move section No. 1 to the line position on the shaft of No. 3, and
No. 3 to that of No. 1, No. 2 remaining stationary. The effect of
this interchange will be that (having regard to the circle of
rotation) No. 3, the rearmost section, will rotate in advance of
No. 2, and No. 2 in advance of No. 1 (see Fig. C). By this
arrangement the water operated on escapes freely astern from every
blade—that from No. 1 passing in the wake of No. 2, while
that from Nos. 2 and 1 passes in the wake of No. 3. Fig. D
represents the blades with a wider spread as practically used. The
advantages claimed by Mr. Dickinson for his propeller, and which
are sufficiently important to be given in detail, are:

Figs. A-D.

1. That the blades of each section, when the vessel is in
motion, necessarily cut solid, undisturbed water, each blade
operating upon precisely the same quantity of water as an
individual broad blade would do, though, of course, it parts with
it in one-third of the time.

2. That each sectional blade exerts the equivalent efficiency of
the first or entering third portion of the breadth of an ordinary
propeller blade, and that consequently the combined sections have
greater effective power. It is now regarded by experts as an
ascertained fact that the after or trailing portion of the broad
blade is relatively non-effective as compared with the forward or
entering portion.

3. When three blades are fitted, the spent water from No. 2
being delivered immediately in the wake of No. 3, and that from No.
1 in the wake of No. 2, has the effect of destroying or reducing to
a minimum the back draught of sections Nos. 2 and 3, No. 1 alone
being subject to this drawback. This is of greater importance than
might at first thought appear, as in cases where there are three or
four blades revolving in one plane, the water is drawn after the
retreating blade, lessening the resistance to the face of the
advancing one.

4. That by the subdivision of the blades, as arranged spirally,
the water passing through within the radius of the propeller has
its resisting capacity more thoroughly worked out than is possible
with any propeller whose blades are all on the same plane. This
view is confirmed by the visibly increased rotation of the water in
the wake of the vessel.

5. That by broadening the blades or increasing the number of
sections, the diameter of the propeller may be proportionately
diminished without the sacrifice of engine power. This is often
desirable with vessels of light draught, the complete immersion of
the screw being at all times necessary to avoid waste of power.

6. The propeller being made and fitted on the shaft in sections,
all that is necessary in case of accident is to replace the broken
section. This in many cases could be done afloat.

7. The blades being arranged to take their water at different
planes, there is the greater certainty of one or other of the
sections operating upon what is termed the water of friction. This
is considered an advantage.

8. Where it is desirable, the blades of the different sections
can be made of varying breadth or pitch.

9. The principle of division into two or more sections applies
equally to two, three, or four bladed ordinary propellers.

10. The adoption of this principle does not entail any
alteration or enlargement of the screw space or bay as usually
provided.

11. As a consequence of the freedom and rapidity with which the
water operated upon escapes from the narrow blades, the depression
at the stern of the vessel caused by the action of the ordinary
propeller is greatly reduced.

12. The vibration caused by this propeller is so slight as to be
hardly noticeable, thereby effecting a saving in the wear and tear
of the engine and machinery. This may also be a consideration in
promoting the comfort of passengers.

From a practical and working point of view we take Mr.
Dickinson’s chief claims to be, in the first place, the yielding of
a greater speed per power employed, or an economy in obtaining an
equal speed; in the second, increased, rapidity in maneuvering and
stopping a vessel; and in the third, a reduction of vibration. In
order to put these claims to a practical and reliable comparative
test, Messrs. Weatherley, Mead & Hussey, of Saint Dunstan’s
Hill, London, placed at the inventor’s disposal two of their new
steamers, the Herongate and the Belle of Dunkerque. These are in
every respect sister boats, and were built in 1887 by Messrs. Short
Brothers, and engined by Mr. John Dickinson, of Sunderland. The
Herongate was fitted about four months ago with the largest
propeller yet made on Mr. B. Dickinson’s principle, the Belle of
Dunkerque having an ordinary four-bladed propeller of the latest
improved type. Every precaution was taken to place the two vessels
on the same footing for the purpose of a comparative test, which
was recently carried out. Both vessels previously to the trial were
placed on the gridiron, cleaned and painted, their boilers opened
out and scaled, their steam gauges independently tested, and both
vessels loaded with a similar cargo of pitch, the only difference
being that the Herongate carried 11 tons more dead weight and had
one inch more mean draught than the Belle of Dunkerque, while the
former had been running continuously for nine months against the
latter’s two and a half months. On the day of the trial the vessels
were lying in the Lower Hope reach, and it was decided to run them
over the measured mile there with equal pressure of steam. The
order of running having been arranged, the Herongate got under way
first, the Belle of Dunkerque following over the same course.
Steaming down against tide, the Herongate is said to have come
round with remarkable ease and rapidity, and in turning on either
helm, whether with or against tide, to have shown a decided
advantage. Equally manifest, it is stated, was the superiority
shown in bringing up the vessel by reversing, when running at full
speed, thus confirming the very favorable reports previously
received by the owners from their captains since the Dickinson
propeller was fitted to the Herongate. Those who were on board her
state that the vibration was scarcely noticeable. From a statement
submitted to us it is clear that the Herongate had the turn of the
scale against her in dead weight and draught, vacuum, and diagrams
taken, but notwithstanding (making allowance for one faulty run due
to the variations in tide) she appears to have more than held her
own in the matter of speed, with a saving of 4½ and
3¼ revolutions per minute at 140 lb. and 160 lb. steam
pressure respectively. This is further confirmed by the results of
a run made after the experiments were concluded, the two vessels
being placed in line, and fairly started for a half hour’s run over
the flood with 150 lb. steam pressure. At the expiration of that
time the Herongate was judged to be leading by at least half a
length, her revolutions being 76, as against 80 in the Belle of
Dunkerque. It was agreed by all present at these trials that the
propeller had realized in full the three main working advantages
claimed for it. This being the first Dickinson propeller fitted to
a sea-going vessel of this size, it is quite within the limits of
possibility that the present results may be improved upon in
further practice. In any case we can but regard this propeller as a
distinct and original departure in marine propulsion, and we
congratulate Mr. Dickinson on his present success and promising
future. Messrs. Weatherley, Mead & Hussey also deserve credit
for their discernment, and for the spirited manner in which they
have taken up Mr. Dickinson’s ingenious invention. We understand
that they are so satisfied with the results that they intend having
one of their larger ocean-going steamers fitted with the Dickinson
propeller.—Iron.

IMPROVED DOBBY.

IMPROVED DOBBY.

At the Manchester Royal Jubilee Exhibition, Messrs. Butterworth
& Dickinson, Burnley, showed Catlow’s patent dobby, which is
illustrated above, as applied to a strong calico loom. This dobby
is a double lift one, thus obtaining a wide shed, and the use of
two lattice barrels connected by gearing so that they both revolve
in the same direction. The jack lever is attached to the vertical
levers, the top and bottom catches being worked respectively by the
two barrels, and connected with the ends of the levers. To each of
these catches a light blade spring is attached, which insures them
being sprung upon the top of the knife, and thereby obtaining a
certain lift. A series of wooden jacks or levers are employed, so
as to give a varying lift to the front and back healds, in this way
keeping the yarn in even tension, and preventing slack sheds. The
healds are drawn down by means of a series of levers adjoining one
another, and worked by means of a rocking bar driven from the
tappet shaft. When the shed is being formed, the jacks are pushed
down until it is fully open, and the warp is thus drawn down with
the same certainty as the upward movement is
made.—Industries.

[United States Consular
Reports. Special Issue No. 10.]

SULPHUR MINES IN SICILY.

By Phillip Carroll, U. S. Consul,
Palermo.

Sulphur, or brimstone, is a hard, brittle substance of various
colors, from brilliant yellow to dark brown, without smell when
cool, of a mild taste, and burns with a pale blue flame, emitting
pungent and suffocating fumes. Its specific gravity is from 1.9 to
2.1.

Sulphur exists more or less in all known countries, but the
island of Sicily, it is thought, is the only place where it is
produced on a large scale, and consequently that island appears to
command the market. Small quantities have been found in the north
of Italy, the Grecian Archipelago, Russia, Austria, Poland, France,
Spain, eastern shores of Egypt, Tunis, Iceland, Brazil, Central
America, and the United States. Large quantities are said to exist
in various countries of Asia, but it is understood to be
impracticable to utilize the same, consequent upon the distance
from any commercial port and the absence of rail or other
roads.

Sulphur is of two kinds, one of which is of volcanic emanation,
the other being closely allied to sedimentary rocks. The latter is
found in Sicily, on the southern and central portions of the
island. Mount Etna, situated in the east, seems to exert no
influence in the formation of brimstone. There are various
hypotheses relative to its natural formation. Dr. Philip
Swarzenburg attributes it to the emanations of sulphur vapor
expelled from metallic matter existing in the earth, consequent
upon the fire in the latter, while Professors Hoffman and Bischoff
ascribe it to the decomposition of sulphureted hydrogen. Hoffman
believes the sulphureted hydrogen must have passed through the
fissures of stratified rocks, but Bischoff is of opinion that the
sulphureted hydrogen must have been the result of the decomposition
of sulphate of lime in the presence of organic matter. The theory
of others is that sulphur owes its origin to the combination of
lacustrine deposits with vegetable matter, and others again suppose
that it is due to the action of the sea upon animal remains. The
huge banks of rock salt often met with in the vicinity of sulphur
mines, and which in some places stretch for a distance of several
miles, seem to indicate that the sea has worked its way into the
subsoil. Fish and insects, which are frequently found in strata of
tripoli, which lie under sulphur beds, induce the belief that lakes
formerly existed in Sicily.

The following is a list of the various strata which form part of
the crust of the earth in Sicily, according to Professor Mottura,
an Italian geologist:

Pliocene.—Sandstone; coarse calcareous rock;
marl.

Upper Miocene.—Calcareous marl; gypsum, etc.;
sulphur embedded in calcareous limestone; silicious limestone;
tripoli, containing fossils of fish, insects’ eggs, etc.

Middle Miocene.—Sandstone containing quartz,
intercalated with marl of a saltish taste.

Lower Miocene.—Rock salt; blue marl, containing
petroleum and bitumen; flintstone; ferruginous clay, mixed with
aragonite and bituminous schists; ferruginous and silicious
sandstone.

Eocene.—Limestone, containing diaspores and
shells.

At times one or another of the strata disappears, while the
order of some is slightly reversed on account of the broken state
of the crust. Upon the whole, however, the above has been generally
observed in the various mines by the author referred to.

Sulphur mines have been operated in Sicily over three hundred
years, but until the year 1820 its exportation was confined to
narrow limits. At present the number of mines existing in Sicily is
about three hundred, nearly two hundred of which, being operated on
credit, are, it is understood, destined to an early demise. It is
said that there are about 30,000,000 tons of sulphur in Sicily at
present, and that the annual production amounts to about 400,000
tons. If this should be true, taking the foregoing as a basis, the
supply will become exhausted in about seventy-five years.

In 1819 a law was passed in Italy, which is still in force,
governing mining in Sicily, which provides that should a land owner
discover ore in his property he would be the owner thereof, and
should have the right to mine, operate, or rent the property to
others for that purpose, but if he should decline to operate his
mines or to rent them to others to be operated, the state would
rent them on its own account.

Royalties vary from 12 to 45 per cent. They are paid according
to the quality of the ore and the facilities for producing sulphur;
25 per cent. may, however, be taken as an average. There is a land
tax of 36 per cent. of the net income, which is usually paid by the
owners and lessees of the mines, in proportion to the quantity of
sulphur which they produce. The export duty is 10 lire per ton. All
mines are inspected by government officials once a year, and the
owners are required to furnish the state with plans of the works
and their progress, with a view to insure the safety of the workmen
and to ascertain the extent of the property.

Those who rent their mines receive from 10 to 40 per cent. of
the sulphur produced. Leases are valid for such period as the
contracting parties may stipulate therein. The general limit,
however, is nine years. The average lease is 25 per cent., 40 per
cent. being paid only when the mines are very favorably situated
and the production good. Some lessees prefer paying a considerable
sum in cash in advance, at the beginning of the term of the lease,
and giving 15 or 20 per cent. in sulphur annually thereafter,
instead of a higher percentage.

The external indications of the presence of sulphur are the
appearance of gypsum and sulphurous springs. These are indubitable
signs of the presence of sulphur, and when discovered the process
resorted to here, in order to reach the sulphur, is to bore a hole
sufficiently large to admit a man, after which steps are
constructed in the passage in order to facilitate the workmen in
going to and fro. These steps extend across the passage, and are
about 25 centimeters high and 35 broad. The inclination of the
holes or passages varies from 30 to 50 degrees. Upon attaining the
depth of several meters water is often met with, and in such
considerable quantity that it is impossible to proceed. Hence it
becomes necessary to either pump the water out or retreat in order
to bore elsewhere. It is often necessary to bore several passages
in order to discover the ore or seam of sulphur. When, however, it
has been discovered the passages are made to follow its direction,
whether upward or downward. As the direction of seams is in most
cases irregular, that of the passages or galleries is likewise.
Where the ore is rich and the matrix yielding, the miners break it
by means of pick-axes and pikes, but when such is not the case
gunpowder is resorted to, the ore in this case being carried to the
surface by boys. The miners detach the ore from the surrounding
material, and the cavities which ensue in consequence assume the
appearance of vast caves, which are here and there supported by
pillars of rock and ore in order to keep them from falling or
giving way. In order to strengthen the galleries sterile rock is
piled upon each side and cemented with gypsum. In extensive mines,
however, these supports and linings are too weak, and not
infrequently, as a result, the galleries and caverns give way,
occasionally causing considerable havoc among the miners. Sulphur
is found from the surface to a depth of 150 meters. The
difficulties met with in operating mines are numerous, and among
the greatest in this category are water, land slides, irregularity
of seam, deleterious gases, hardness of rocks and matrices. Of
these difficulties, water is the most frequently met with. Indeed,
it is always present, and renders the constant use of pumps
necessary. At one time miners were allowed to dig where they
pleased so long as sulphur was extracted, the consequence being
that in groups of mines, the extent and direction of which being
unknown to their respective owners, one mine often fell into or
upon another, thus causing destruction to life and property. It was
largely for this reason, it is understood, that the government
determined to require owners and lessees of mines to furnish plans
thereof to proper authority, and directed that official inspection
of the mines should be made at stated periods. In order to comply
with the decree of the government it became necessary to employ
mining engineers to draw the plans, etc., and those employed were
generally foreigners. In the system of excavation described no
steam power is employed. Pumping is performed by means of primitive
wooden hand pumps, and when sufficient ore has been collected it is
conveyed on the backs of boys to the surface—a slow, costly,
and difficult procedure. This system may, however, be suitable to
small mines, but in large mines there is no economy in hand labor;
indeed, much is lost in time and expense by it. For this reason
steam has been introduced into the larger and more important mines.
The machinery employed is a hoisting apparatus, with a drum, around
which a coil is wound, with the object of hoisting and lowering
trucks in vertical shafts. Steam pumps serve to extract the water.
The force of the hoisting apparatus varies from 15 to 50 horse
power. The fuel consumed is English and French coal, the former
being preferred, as it engenders greater heat. The cost of a ton of
coal at the wharf is $4.40, whereas in the interior of the island
it costs about $10. The shafts or pits are made in the ordinary
way, great care being taken in lining them with masonry in order to
guard against land slides. In level portions of the country
vertical shafts are preferred, but where the mine is situated upon
a hill a debouch may often be found below the sulphur seam, when an
inclined plane is preferred, the ore being placed in trucks and
allowed to run down the plane on rails until it reaches the
exterior of the mine, where it suddenly and violently stops, and as
a result the trucks are emptied of their load, when they are drawn
up the plane to be refilled; and thus the process goes on
indefinitely. In these mines a gutter is made in the inclined plane
which carries off the water, thus dispensing with the necessity of
a pump and the requisites to operate it. The galleries and inclined
shafts are lined with beams of pine or larch, which are brought
hither from Sardinia, as Sicily possesses very little timber. The
mines are illuminated by means of iron oil lamps, the wicks of
which are exposed. The lamps are imported from Germany. In certain
cases an earthenware lamp, made on the island, and said to be a
facsimile of those used by the Phœnicians, is employed. This
lamp is made in the shape of a small bowl. It is filled with oil
and a wick inserted, which hangs or extends outward, and is thus
ignited, the flame being exposed to the air. Safety lamps are
unknown, and those described are generally secure. Few explosions
take place—only when confined carbonic hydrogen is met with
in considerable quantities, and when the ventilation is not good.
In this case the mine is easily ignited, and once on fire may burn
for years. The only practical expedient for extinguishing the fire
is to close all inlets and outlets in order to shut off the air.
This, however, is difficult and takes time. Notwithstanding the
closing of communications, the gases escape through the fissures
and openings which obtain everywhere, and the ingress of air makes
it next to impossible to extinguish the fire; hence it burns
indefinitely or until the mine is exhausted. Occasionally the
burning of a mine results beneficially to its owners, in that it
dispenses with the necessity of smelting, and produces natural,
refined sulphur.

Galleries in extent are usually 1.20 by 1.80 meters, and when
ore is not found and it becomes necessary to extend the galleries,
laborers are paid in accordance with the progress they may make and
the character of the rock, earth, etc., through which it may be
necessary to cut, as follows:

Silicious limestone, 60 lire per meter; daily progress, 0.20
meter.

Gypsum, 50 lire per meter; daily progress, 0.30 meter.

Marl, 30 lire per meter; daily progress, 0.50 meter.

Clay, 15 lire per meter; daily progress, 1 meter.

Laborers working in the ore are paid 4.30 lire per ton. This
includes digging, extracting, and illumination. In some mines,
however, the laborers are paid when the sulphur is fused and ready
for exportation. One ton of sulphur, or its equivalent (say from 40
to 50 lire), is the amount generally paid. In mines where this
system obtains the administration is only responsible for their
maintenance. Each miner produces on an average about 1½ tons
of ore daily, and when the works are not more than 40 meters in
depth he employs one boy to assist him, two boys when they reach 60
meters, and three when under 100 meters. These boys are from seven
to sixteen years of age, and are paid from 0.85 to 1.50 lire per
day by the miner who employs them. They carry from 1,000 to 1,500
pounds of ore daily, or in from six to eight hours. The food
consumed by miners is very meager, and consists of bread, oil,
wine, or water; occasionally cheese, macaroni, and vegetables are
added to the above.

Mining laborers generally can neither read nor write, and when
employed in mines distant from habitations or towns, live and sleep
therein, or in the open air, depending on the season or the
weather. In a few mines the laborers are, however, provided with
suitable dwelling places, and a relief fund is in existence for the
succor of the families of those who die in the service. This fund
is greatly opposed by the miners, from whose wages from 1 to 2 per
cent. is deducted for its maintenance. In the absence of a fund of
this character, the sick or infirm are abandoned by their
companions and left to die. Generally miners are inoffensive when
fairly dealt with. They are said to be indolent and dishonest as a
rule. The managers of mines receive from 3,000 to 5,000 lire per
annum; chief miners from 1,500 to 2,500 lire; surveyors, 700 to
1,000 lire; and weighers and clerks, from 1,000 to 2,000 lire per
annum. The total number of mining laborers in Sicily is estimated
at about 25,000.

The ore for fusion of the first grade as to yield contains from
20 to 25 per cent. of sulphur, that of the second grade from 15 to
20 per cent., and of the third grade 10 to 15 per cent. The usual
means adopted for extracting sulphur from the ore is heat, which
attains the height of 400 degrees Centigrade, smelting with the
kiln, which in Sicilian dialect is called a “calcarone.” The
“calcarone” is capable of smelting several thousand tons of ore at
a time and is operated in the open air. Part of the sulphur is
burned in the process of smelting in order to liquefy the
remainder. “Calcaroni” are situated as closely to the mouth of a
shaft as possible, and if practicable on the side of a hill, in
order that when the process of smelting is complete, the sulphur
may run down the hill in channels prepared for the purpose. The
shop of a “calcarone” is circular and the floor has an inclination
of from 10 to 15 degrees. A design of a “calcarone” is herewith
inclosed. The circular wall is made of rude stone work, cemented
together with gypsum. The thickness of the wall at the back is 0.50
meter, and from this it gradually becomes thicker until in front,
where it is 1 meter, when the diameter is to be 10 meters. In front
of the thickest part of the wall an opening is left, measuring 1.20
meters high and 0.25 meter broad.

Through this opening the liquid sulphur flows. Upon each side of
this opening two walls are built at right angles with the circular
wall, in order to strengthen the front of the kiln. These walls are
80 centimeters thick each and are roofed. A door is hinged to these
walls, thus forming a small room in front of each kiln in which the
keeper thereof resides from the commencement to the termination of
the flow of sulphur. The inclined floor of the kiln is made of
stone work and is covered with “ginesi,” the name given to the
refuse of a former process of smelting. The stone work is 20
centimeters thick, and the “ginesi” covering 25 centimeters, which
gradually becomes thicker as it approaches its lowest extremity.
The front part of the circular wall is 3.50 meters high and the
back 1.80 meters. The interior of the wall is plastered with gypsum
in order to render it impermeable.

The cost of a “calcarone” of about 500 tons capacity is 800
lire. The capacity varies from 40 to 5,000 tons, or more, depending
upon circumstances. If a mine is enabled to smelt the whole year
round, the smaller “calcaroni,” being more easily managed, are
preferred; the inverse is the case as to the larger “calcaroni,”
when this is impracticable. When a “calcarone” is situated within
100 meters of a cereal farm, its operation is prohibited by law
during the summer, lest the fumes of the sulphur should destroy the
crop.

When, however, the distance is greater from the farm or farms
than 100 meters, smelting is permitted; but should any damage ensue
to the crops as a result of the fumes, the owners of the
“calcaroni” are required to liquidate it. Therefore the mines which
are favorably situated smelt the entire year, and employ
“calcaroni” of from 40 to 500 tons, as there is less risk of a
process failing, which occasionally happens, and for the reason
that the ore can be smelted as soon as it is extracted; whereas,
when kilns or “calcaroni” are situated within or adjacent to the
limit adverted to, they can only be operated five or six months in
the year, consequent upon which the ore is necessarily stacked up
all through the summer or until such time as smelting may be
commenced without endangering the crops, when it becomes necessary
to use “calcaroni” whose capacity amounts to several thousand tons.
As intimated, these large “calcaroni” are not so manageable as
those of smaller dimensions, and as a result many thousands of tons
of sulphur are lost in the process of smelting, besides perhaps the
loss of an entire year in labor. Again, the ore deteriorates or
depreciates when long exposed to the air and rain, all of which,
when practicable, render the kilns or “calcaroni” of the smaller
capacity more advantageous and lucrative to those operating sulphur
mines in Sicily. Smelting with a “calcarone” of 200 tons capacity
consumes thirty days, one of 800 tons 60 days, and with a
“calcarone” of 2,000 tons capacity from 90 to 120 days are
consumed.

In loading or filling the “calcaroni,” the larger blocks of ore
are placed at the bottom as well as against the mouth, in order to
keep the lower part of the kiln as cool as possible with a view of
preventing the liquid sulphur from becoming ignited as it passes
down to where it makes its exit, etc. The blocks of ore thus first
placed in position are, for obvious reasons, the most sterile.
After the foundation is thoroughly laid the building of the “pile”
is proceeded with, the larger blocks being placed in the center to
form, as it were, the backbone of the pile; the smaller blocks of
ore are arranged on the outside of these and in the interstices.
The shape or form of the pile when completed is similar to a
truncated cone, and when burning the kiln looks like a small
volcano. When the kiln has been filled with ore, the whole is
covered with ginesi with a view of preventing the escape of the
fumes. The ore is then ignited by means of bundles of straw,
impregnated or saturated with sulphur, being held above the thin
portion of the top of the kiln, which is at once closed with
ginesi, and the “calcarone” is left to itself for about a week.
During the burning process the flames gradually descend, and the
sulphur contained in the ore is melted by the heat from above. In
about seven or eight days sulphuric fumes and sublimed sulphur
commence to escape, when it becomes necessary to add a new coat of
ginesi to the covering and thus prevent the destruction of
vegetation by the sulphur fumes. The mouth of the kiln, which has
been left open in order to create a draught, is closed up about
this time with gypsum plaster. When the sulphur is all liquefied it
finds its way to the most depressed part of the kiln, and there,
upon encountering the large sterile blocks, quite cold, already
referred to, solidifies. It is again liquefied by means of burning
straw, whereupon an iron trough is inserted into a mouth made in
the kiln for the purpose, and the reliquefied sulphur runs into it,
from which it is immediately collected into wooden moulds, called
“gadite,” and which have been kept cool by being submerged in
water. Upon its becoming thoroughly cool the sulphur is taken out
of the moulds referred to, and is now in solid blocks, each
weighing about 100 weight. Two of these blocks constitute a load
for a mule, and cost from 4 to 5 francs.

The above is the result when the operation succeeds; but this is
not always the case. At times the sulphur becomes solidified before
it reaches the mouth of the kiln, because of the heat not being
sufficient to keep it liquid in its passage thereto, and other
misfortunes not within control, and consequent upon the use of the
larger kilns, or “calcaroni.”

When the sulphur ceases to run from the kiln, the process is
complete. The residue is left to cool, which consumes from one to
two months. The cooling process could be accomplished in much less
time by permitting the air to enter the kiln, but this would be
destructive to vegetation, and even to life, consequent upon the
fumes of the sulphur. The greatest heat at a given time in a kiln
is calculated to be above 650 degrees Centigrade—that is, at
the close of the process. This enormous heat is generally allowed
to waste, whereas it is understood it could be utilized in many
ways. A gentleman of the name of Gill is understood to have
invented a recuperative kiln, which will, if generally adopted,
utilize the heat of former processes named. A ton of ore containing
about 25 per cent. of sulphur yields 300 pounds of sulphur. This is
considered a good yield. When it yields 200 pounds it is considered
medium, and poor when only 75 pounds. Laborers are paid 0.40 lire
per ton for loading and unloading kilns, and from thirty to forty
hands are employed at a time. The keeper of a kiln receives from 2
to 2.50 lire per day.

Notwithstanding the “calcarone” has many defects, it is the
simplest and cheapest mode of smelting, and is preferred here to
any other system requiring machinery and skilled labor to operate
it.

The following are the principal furnaces in use here: Durand’s;
Hirzel; Gill and Kayser’s system of fusion; Conby Bollman process;
Thomas steam process of smelting; and Robert Gill’s recuperative
kilns.

There are seven qualities or grades of sulphur, viz.:

1. Sulphur almost chemically pure, of a very bright and yellow
color.

Second Best.—Slightly inferior to the first
quality; bright and yellow.

Second Good.—Contains 4 to 5 per cent. of earthy
matter, but is of a bright yellow.

Second Current.—Dirty yellow, containing more
earthy matter than that last named.

Third Best.—Brownish yellow; this tint depends on
the amount of bitumen which it contains.

Third Good.—Light brown, containing much extraneous
matter.

Third Current.—Brown and coarse.

These qualities are decided by color, not by test. The
difference of price is from 3 to 10 francs per ton. Manufacturers
prefer the third best, because of its containing more sulphuric
acid and costing less than the sulphur of better quality.

Sulphur is conveyed to the seaboard by rail, in carts, or on
mules or donkeys. Conveyance by cart, mule, or donkey is only
resorted to when the distance is short or from mines to railroad
stations. The tariff in the latter case is understood to be 1 lire
per ton per mile. The railroad tariff is 0.12 per ton per
kilometer; but it is contemplated, it is understood, to reduce this
to 7 centimes in a short time. The price per ton of sulphur is as
follows:

Sulphur free on board, brokerage, shipment, export duty, and all
other expenses included, costs 20 lire per ton in excess of the
above prices. Nearly all the sulphur exported from Palermo emanates
from the Lercara mines, in the province of Palermo, the price per
ton being as follows: first quality, 91.60 lire; second quality,
88.40. Sulphur is usually conveyed in steamers to foreign countries
from Sicilian ports. The average freight per ton to New York is
about as follows: From Palermo, 8.70 lire; from Catania, 13.50
lire; from Girgenti, 16 lire. An additional charge of 2.50 lire is
made when the sulphur may be destined for other ports in the United
States.

Liebig once said that the degree of civilization of a nation and
its wealth could be seen in its consumption of sulphuric acid. Now,
although Italy produces immense quantities of sulphur, it cannot,
on account of the scarcity of fuel, and other obvious reasons
perhaps, compete with certain other countries in the manufacture
and consumption of sulphuric acid.

Sulphur is employed in the manufacture of sulphuric acid, and
the latter serves in the manufacture of sulphate of soda, chloridic
acid, carbonate of soda, azodic acid, ether, stearine candles,
purification of oils in connection with precious metals and
electric batteries. Nordhausen’s sulphuric acid is employed in the
manufacture of indigo. Sulphate of soda is employed in the
manufacture of artificial soda, glassware, cold mixtures, and
medicines. Carbonate of soda is used in the manufacture of soap,
bleaching wool, coloring and painting tissues, and in the
manufacture of fine crystal ware and the preparation of borax.
Chloric acid is used in the preparation of chlorides with bioxide
of manganese, and with chlorides in the preparation of
hypochlorides of lime, known in commerce under the name of
bleaching powder, and improperly called chloride of lime, which is
used as a disinfectant in contagious diseases, in bleaching stuffs,
and in the manufacture of paper from vegetable fibers, and in the
manufacture of gelatine extracted from bones, as well as in
fermenting molasses and in the manufacture of sugar from beet root.
Sulphur is also used in the preparation of gunpowder and oil of
vitriol, and in the manufacture of matches and cultivation of the
vine.

In the year 1838 the Neapolitan government granted a monopoly to
a French company for the trade in sulphur. By the terms of the
agreement the producers were required to sell their sulphur to the
company at certain fixed prices, and the latter paid the government
the sum of $350,000 annually in consideration of this requirement.
This, however, was not a success, and tended to curtail the sulphur
industry, and the government, discovering the agreement to be
against its interests, annulled it, and established a free system
of production, charging an export tax per ton only. At that time
sulphuric acid was derived exclusively from sulphur. Hence the
demand from all countries was great, and the prices paid for
sulphur were high. It was about this period that the sulphur
industry was at its zenith. The monopoly having been abolished,
every mine did its utmost to produce as much sulphur as possible,
and from the export duty exacted by the government there accrued to
it a much larger revenue than that which it received during the
period of the monopoly. The progress of science has, however,
modified the state of things since then, as sulphur can now be
obtained from pyrite or pyrite of iron. This discovery immediately
caused the price of sulphur to fall, and the great demand therefore
correspondingly ceased. In England, at the present time, it is
understood that two-thirds of the sulphuric acid used is
manufactured from pyrites. The decrease in prices caused many of
the mines to suspend operations, and as a result the sulphur
remained idle in stock. In 1884 an association was formed at
Catania with a view to buying up sulphur thus stored away at the
mines and various ports at low prices, and store it away until a
favorable opportunity should present itself for the sale thereof.
This had the effect of increasing the prices of sulphur in Sicily
for some time, and the producers, discovering that the methods of
the association increased the foreign demand for their produce as
well as its prices, exported it directly themselves, thus breaking
up the association referred to, as it was no longer a profitable
concern.

The railroad system, which in later years has placed the most
important parts of Sicily in communication with the seaboard, has
been most beneficial to the sulphur industry. A great saving has
been made in transporting it to the ports. This was formerly (as
stated) accomplished by carts drawn by mules at an enormous
expense, as the roads were wretched, and unless some person of
distinction contemplated passing over them, repairs were
unknown.

Palermo, March 20, 1888.

AN AUTOMATIC STILL.

By T. Maben.

The arrangement here described is one that may readily be
adapted to, and is specially suited for, the old fashioned stills
which are in frequent use among pharmacists for the purpose of
distilling water. The idea is extremely simple, but I can testify
to its thorough efficiency in actual practice. The still is of
tinned copper, two gallon capacity, and the condenser is the usual
worm surrounded with cold water.

The overflow of warm water from the condenser is not run into
the waste pipe as in the ordinary course, but carried by means of a
bent tube, A, B, C, to the supply pipe of the still. The bend at B
acts as a trap, which prevents the escape of steam.

The advantages of this arrangement are obvious. It is perfectly
simple, and can be adapted at no expense. It permits of a
continuous supply of hot water to the still, so that the contents
of the latter may always be kept boiling rapidly, and as a
consequence it condenses the maximum amount of water with the
minimum of loss of heat. If the supply of water at D be carefully
regulated, it will be found that a continuous current will be
passing into the still at a temperature of about 180° F., or,
if practice suggest the desirability of running in the water at
intervals, this can be easily arranged. It is necessary that the
level at A should be two inches or thereabout higher than the level
of the bend at C, otherwise there may not be sufficient head to
force a free current of water against the pressure of steam. It
will also be found that the still should only contain water to the
extent of about one-fourth of its capacity when distillation is
commenced, as the water in the condenser becomes heated much more
rapidly than the same volume is vaporized. By this expedient a
still of two gallons capacity will yield about half a dozen gallons
per day, a much greater quantity than could ever be obtained under
the old system, which required the still to be recharged with cold
water every time one and a half gallons had been taken off.

The objection to all such continuous or automatic arrangements
is, of course, that the condensed water contains all the free
ammonia that may have existed in the water originally, but it is
only in cases where the water is exceptionally impure that this
disadvantage will become really serious. The method here outlined
has, no doubt, occurred to many, and may probably be in regular
use, but not having seen any previous mention of the idea, I have
thought that it might be useful to some pharmacists who prepare
their own distilled water.—Phar. Jour.

COTTON SEED OIL.

“Cotton seed oil,” said Mr. A.E. Thornton, of the Atlanta mills,
“is one of the most valuable of oils because it is a neutral oil,
that is, neither acid nor alkali, and can be made to form the body
of any other oil. It assimilates the properties of the oil with
which it is mixed. For instance, olive oil. Cotton seed oil is
taken and a little extract of olives put in. The cotton oil takes
up the properties of the extract, and for all practical purposes it
is every bit as good as the pure olive oil. Then it is used in
sweet oil, hair oil, and, in fact, in nearly all others. A chemist
cannot tell the prepared cotton oil from olive oil except by
exposing a saucerful of each, and the olive oil becomes rancid much
quicker than the cotton oil. The crude oil is worth thirty cents a
gallon, and even as it is makes the finest of cooking lard, and
enters into the composition of nearly all lard.”

A visit to the mills showed how the oil is made. From the
platform where the seed is unloaded it is thrown into an elevator
and carried by a conveyor—an endless screw in a
trough—to the warehouse. Then it is distributed by the
conveyor uniformly over the length of the building—about 200
feet. The warehouse is nearly half filled now, and thousands and
thousands of bushels are lying in store. Another elevator carries
the seed up to the “sand screen.” This is a revolving cylinder made
of wire cloth, the meshes being small enough to retain the seed,
which are inside the cylinder, but the sand and dirt escape. Now
the seeds start down an inclined trough. There is something else to
be taken out, and that is the screws and nails and rocks that were
too large to be sifted out with the sand and dirt. There is a hole
in the inclined trough, and up through that hole is blown a current
of air by a suction fan. If it were not for the fan, the cotton
seed, rocks, nails, and all would fall through. The current keeps
up the cotton seed, and they go on over, but it is not strong
enough to keep up the nails and pebbles, and they fall through. Now
the seed, free of all else, is carried by another elevator and
endless screw conveyor to the “linter.” This is really nothing more
than a cotton gin with an automatic feed.

“HULLER” AND “HEATERS.”

Then the seed is carried to the “huller,” where it is crushed or
ground into a rough meal about as coarse as the ordinary corn
“grits.” The next step is to separate the hulls from the kernels,
all the oil being in the kernel, so the crushed seed is carried to
the “separator.” This is very much on the style of a sand screen,
being a revolving cylinder of wire cloth. The kernels, being
smaller than the broken hulls, fall through the broken meshes, and
upon this principle the hull is separated and carried direct to the
furnace to be used as fuel. The kernels are ground as fine as meal,
very much as grist is ground, between corrugated steel “rollers,”
and the damp, reddish colored meal is carried to the “heater.”

The “heater” is one iron kettle within another, the six inch
steam space between the kettles being connected direct with the
boilers. There are four of these kettles side by side. The meal is
brought into this room by an elevator, the first “heater” is
filled, and for twenty minutes the meal is subjected to a “dry
cook,” a steam cook, the steam in the packet being under a pressure
of forty-five pounds. Inside the inner kettle is a “stirrer,” a
revolving arm attached at right angles to a vertical shaft. The
stirrer makes the heating uniform, and the high temperature drives
off all the water in the meal, while the involatile oil all
remains.

In five minutes the next heater is filled, in five minutes the
next, etc.

Now there are four “heaters,” and as the last heater is
filled—at the end of twenty minutes—the first heater is
emptied. Then at the end of five minutes the first heater is
filled, and the one next to it is emptied, and the rotation is kept
up, each heater full of meal being “dry-cooked” for twenty
minutes.

Corresponding to the four heaters are four presses. Each press
consists of six iron pans, shaped like baking pans, arranged one
above the other, and about five inches apart. The pans are shallow,
and around the edge of each is a semicircular trough, and at the
lowest point of the trough is a funnel-shaped hole to enable the
oil to run from one pan to the next lowest, and from the lowest pan
to the “receiving tanks” below.

PRESSING OUT THE OIL.

As soon as a “heater” is ready to be emptied, the meal is taken
out and put into six hair sacks, corresponding to the six pans in
the press. There are six hair mats about one foot wide and six
long, one side of each being coated with leather. The hair mat is
about an inch thick. Now the hair sack, containing ten and a half
to eleven pounds of heated steaming meal, is placed on one end of
the mat, and the meal distributed so as to make a pad or cushion of
uniform thickness. The pad of meal is not quite three feet long, a
foot wide, and three inches thick, and the hair mat is folded over,
sandwiching the pad and leaving the leather coating of the pad
outside. In this form the six loads are put into the six pans, and
by means of a powerful hydraulic press the pans are slowly pressed
together. The oil begins trickling out at the side, slowly at
first, and then suddenly it begins running freely. The pressure on
the “loads” is 350 tons. After being pressed about five minutes,
the pressure is eased off and the “loads” taken out. What had been
a mushy pad three inches thick is a hard, compact cake about
three-quarters of an inch thick, and the sack is literally glued to
the cake. The crude oil has a reddish muddy color as it runs into
the tanks.

To one side were lying great heaps of sacks of yellowish
meal—the cakes which have been broken and ground up into
meal. That, as explained above, forms the body of all fertilizers.
The following is a summary of the work for the eight months’ season
at the Atlanta mills:

Fifteen thousand tons of seed used give:

Fifteen million pounds of hull.

Ten million three hundred and thirty-one thousand two hundred
and fifty pounds of meal.

Four million six hundred and sixty-eight thousand seven hundred
and fifty pounds of oil.

Three hundred thousand pounds of lint cotton.

The meal is worth at the rate of $6 for 700 pounds, or
$88,603.58.

The oil is worth thirty cents a gallon, or seven and a half
pounds, or $186,750.

The lint is worth $18,000, making a total of $293,353, and that
doesn’t include the 15,000,000 pounds of hull.—Atlanta
Constitution.

MANUFACTURE OF PHOTOGRAPHIC SENSITIVE PLATES.

Quite recently Messrs. Marion & Company, London, began on
their own account to manufacture sensitive photographic plates by
machinery, and the operations are exceedingly delicate, for a
single minute air bubble or speck of dust on a plate may mar the
perfection of a picture. Their works for the purpose at Southgate
were erected in the summer of 1886, and were designed throughout by
Mr. Alexander Cowan.

Fig. 1.

Buildings of this kind have to be specially constructed, because
some of the operations have to be carried on in the absence of
daylight, and in that kind of non-actinic illumination which does
not act upon the particular description of sensitive photographic
compound manipulated. Glass and other materials have therefore to
pass from light to dark rooms through double doors or double
sliding cupboards made for the purpose, and the workshops have to
be so placed in relation to each other that the amount of lifting
and the distance of carriage of material shall be reduced to a
minimum. Moreover, the final drying of sensitive photographic
plates takes place in absolute darkness. Fig. 1 is a ground plan of
the chief portion of the works. In this cut, A is the manager’s
private office, B the counting house, C the manager’s laboratory,
and D his dark room for private experiment, which can thus be
conducted without interfering with the regular work of the
establishment. E is the carpenter’s shop and packing room, F the
albumen preparation room, G the engine room, with its two doors;
the position of the engine is marked at H. The main building is
entered through the door, K; the passage, L, is used for the
storage of glass, and has openings in the wall on one side to
permit the passage of glass into the cleaning room, M; this room is
illuminated by daylight. The plates, after being cleaned, pass into
the coating rooms, N and O, into which daylight is never admitted;
the coating machine is in the room, N, and three hand coating
tables in the room, O; both these rooms are illuminated by
non-actinic light.

Fig. 2.

Fig. 3.

The walls of N and O are of brick, to keep these interior rooms
as cool as possible in hot weather, for the making of photographic
plates is more difficult in summer time, because the high
temperature tends to prevent the rapid setting of the gelatine
emulsion upon them. At the end of these rooms and communicating
with both is the lift, P, by which the coated plates are carried to
the drying rooms above, which there cover the entire area of the
main building; they consist of two rooms measuring 60 ft. by 30
ft., and are each 30 ft. high at the highest part in the center of
the building; these rooms are necessarily kept in absolute
darkness, except while the plates are being stored therein or
removed therefrom, and on such occasions non-actinic light is used.
After the plates are dry, they come down the lift, Q, into the
cutting and packing room, R, which is illuminated by non-actinic
light. In the drying rooms the batches of plates are placed one
after the other on tram lines at one end of the room, and are
gradually pushed to the other end of the building, so that the
first batches coated are the first to be ready to be taken off when
dry, and to be sent down the lift, Q. The plates in R, when
sufficiently packed to be safe from the action of daylight, are
passed through specially constructed openings into the outside
packing room, S, where they are labeled. The chemicals are kept in
the room, T, where they are weighed and measured ready for the
making of the photographic emulsion in the room, U. The next room,
V, is for washing small experimental batches of emulsion, and W is
the large washing room. The emulsion is then taken into the
passage, X, communicating with the two coating rooms. A centrifugal
machine in the room, Y, is used for extracting silver residues from
waste materials, also for freeing the emulsion from all soluble
salts. Washing and cleaning in general go on in the room, Z.

Fig. 4.—PLATE-WARMING MACHINE.

The glass for machine coating is cut to standard sizes at the
starting, instead of being coated in large sheets and cut
afterward—a practice somewhat common in this industry. The
disadvantage of the ordinary plan is that minute fragments of glass
are liable to settle upon the sensitive film and to cause spots and
scratches during the packing operations; any defect of this kind
renders a plate worthless to the photographer. When any breakages
take place in the cutting, it is best that they should occur at the
outset, and not after the plate has been coated with emulsion. The
cutting when necessary is effected by the aid of a “cutting board,”
Fig. 2, invented by Mr. Cowan, and now largely in use in the
photographic world. This appliance is used to divide into two equal
parts, with absolute exactness, any plate within its capacity, and
it is especially useful in dimly lighted rooms. It consists of four
rods pivoted together at the corners and swinging on two centers,
so that in the first position it is truly square, and in other
positions of rhomboid form, the two outer bars approaching each
other like those of a parallel ruler. The hinge flap comes down on
the exact center of the plate, minus the thickness of the block
holding the diamond. By this appliance plates can be cut in either
direction. Fig. 3 represents a similar arrangement for cutting a
number of very small plates out of one large one; in this the hinge
flap is made in the form of a gridiron, and the bars are spaced at
accurate distances, according to the size of the plate to be cut,
so that a plate 10 in. square, receiving four cuts in each
direction, will be divided into twenty-five small plates.

Fig. 5.

Before being cleaned all sharp edges are roughly taken off those
plates intended for machine coating by girls, who rub the edges and
corners of the plates upon a stone; the plates are then cleaned by
any suitable method in use among photographers. The plates, now
ready for the coating room, have to be warmed to the temperature of
the emulsion, say from 80 deg. F. to 100 deg. F., before they pass
to the coating machine, the inventor of which, Mr. Cadett, having
come to the conclusion that, if the plates are not of the proper
temperature, the coating given will be uneven over various parts of
the surface. The plate-warming machine is represented in Fig. 4; it
was designed by Mr. A. Cowan, and made by his son, Mr. A. R. Cowan.
It consists of a trough 7 ft. long by 3 in. deep, forming a flat
tank, through which hot water passes by means of the circulating
system shown in the engraving. To facilitate the traveling of the
glass plates without friction the top of the tank is a sheet of
plate glass bedded on a sand bath. An assistant at one end places
the glasses one after the other on the warm glass slab, and by
means of a movable slide pushes them one at a time under the cover,
which cover is represented raised in the engraving to show the
interior of the machine. After having put one glass plate on the
slide, another cannot be added until the man in the dark room at
the other end of the slide has taken off the farthest warmed plate,
because the slide has a reciprocating movement. This heating
apparatus is built at right angles to the coating machine in the
next room, in order to be conveniently placed in the present
building; but it is intended in future to use it as a part of the
coating machine itself, and to drive it at the same speed and with
the same gearing, so that the cold plates will be put on by hand at
one end, get warmed as they pass into the dark room, at the other
end of which they will be delivered by the machine in coated
condition. Underneath the heating table is a copper boiler, with
its Bunsen’s burner of three concentric rings to get up the
temperature quickly and to give the power of keeping the water
under the heating slab at a definite temperature, as indicated by a
thermometer. The cold water tank of the system is represented
against the wall in the cut.

Fig. 6.

Fig. 5 represents the hot water circulating system outside the
coating rooms for keeping the gelatine emulsions in these dimly
lighted regions at a given temperature, without liberating the
products of combustion where the emulsion is manipulated. The
temperature is regulated automatically. It will be noticed where
the pipes enter the two coating rooms, and Fig. 6 shows the copper
inside one of them heated by the apparatus just described. The
emulsion vessel in the copper is surrounded by warm water, and the
copper itself is jacketed and connected with the hot water pipes,
so forming part of the circulating system.

Fig. 7.—GENERAL VIEW OF COATING
MACHINE.

Fig. 7 is a general view of the coating machine recently
invented by Mr. Cadett, of the Greville Works, Ashtead, Surrey. The
plates warmed in the light room, as already described, are
delivered near the end of the coating table, where they are picked
off a gridiron-like platform, represented on the right hand side of
the cut, and are placed by an assistant one by one upon the
parallel gauges shown at the beginning of the machine proper; they
are then carried on endless cords under the coating trough
described farther on. After they have been coated they are carried
onward upon a series of four broad endless bands of absorbent
cotton—Turkish toweling answers well—and this cotton is
kept constantly soaked with cold water, which flows over sheets of
accurately leveled plate glass below and in contact with the
toweling; the backs of the plates being thus kept in contact with
fresh cold water, the emulsion upon them is soon cooled down and is
firmly set by the time the plates have reached the end of the
series of four wet tables. They are then received upon one over
which dry toweling travels, which absorbs most of the moisture
which may be clinging to the backs of the plates; very little wet
comes off the backs, so that during a day’s work it is not
necessary to adopt special means to redry this last endless band.
What are technically known as “whole plates,” which are 8½
in. by 6½ in., are placed touching each other end to end as
they enter the machine, and they travel through it at the rate of
720 per hour; smaller sizes are coated in proportion, the smaller
the plates the larger is the number coated in a given time. The
smaller plates pass through the machine in two parallel rows,
instead of in a single row, so that quarter plates, 4¼ in.
by 3¼ in., are delivered at the end of the machine at the
rate of 2,800 per hour, keeping two attendants well employed in
picking them up and placing them in racks as quickly as they can do
the work. The double row of cords for carrying two lines of small
plates through the machine is represented in the engraving.
Although the plates touch each other at their edges on entering the
machine, they are separated from each other by short intervals
after being coated; this is effected by differential gearing. The
water flowing over the tables for cooling the plates is caught in
receptacles below and carried away by pipes. Between each of the
tables is a little roller to enable small plates to travel without
tilting over the necessary gap between each pair of bands.

Fig. 8.

The feeding trough of Cadett’s machine is represented in Fig. 8.
The plates, cleaned as already described, are carried upon the
cords under a brass roller, the weight of which causes sufficient
friction to keep the plates from tilting; they next pass under a
soft camel’s hair brush to remove anything in the shape of dust or
grit, and are then coated. They afterward pass over a series of
accurately leveled wheels running in a tank of water kept exact by
an automatic regulator at a temperature of from 80 deg. Fah. to 100
deg. Fah., by means of a small hot water circulating system. The
emulsion trough is jacketed with hot water at a constant
temperature. This trough is silver plated inside, because most
metals in common use would spoil the emulsion by chemical action.
The trough is 16 in. long; it somewhat tapers toward the bottom,
and contains a series of silver pumps shown in the cut; the whole
of this series of pumps is connected with one long adjustable crank
when plates of the largest size have to be coated; when coating
plates of smaller sizes some of the pumps are detached. A chief
object of the machine is to deliver a carefully measured quantity
of emulsion upon each plate, and this is done by means of pumps, in
order that the quantity of emulsion delivered shall not be affected
by changes in the level of the emulsion in the trough; the quantity
delivered is thus independent of variations due to gravity or to
the speed of the machine. These pumps draw the emulsion from a
sufficient depth in the trough to avoid danger from the presence of
air bubbles, and the bottom of the trough is so shaped that should
by chance any sedimentary matter be present, it has a tendency to
travel downward, away from the bottoms of the pumps. There is a
steady flow of emulsion from the pumps to the delivery pipes, then
it passes down a guide plate of the exact width of the plate to be
coated. Immediately in front of the guide plate is a fixed silver
cylinder, kept out of contact with the plate by the thickness of a
piece of fine and very hard hempen cord, which can be renewed from
time to time. These cords keep the cylinder from scraping the
emulsion off the plate, and they help to distribute it in an even
layer. There would be two lines upon each plate where it is touched
by the cords, were not the emulsion so fluid as to flow over the
cut-like lines made and close them up.

Fig. 9.

The silver cylinder to a certain extent overcomes the effects of
irregularities in the glass plates, for the cylinder is jointed
somewhat in the cup and ball fashion, and is made in two or more
parts, which parts are held together by lengths of India
rubber.

Fig. 10.

The arrangement is shown in section in Fig. 9, in which A is the
hot water jacket of the emulsion vessel; B, the crank driving the
pumps; C, a pump with piston in position; D, delivery tube of the
pump; E, the silver guide plate to conduct the emulsion down to the
glass; F, the spreading cylinder; G, the cords regulating the
distance of the cylinder from the glass plates; H, soft camel’s
hair brush; K, friction roller; L L L, three plates passing under
the emulsion tank; M, knife edged wheels in the hot water tank, N;
the “plucking roller,” P, has a hot water tank of its own, and
travels at slightly greater speed than the other rollers; R is the
beginning of the cooling bands; T, the driving cords; and W, a
level of the emulsion in the trough. Y represents one of the bucket
pistons of the pumps, detached. The construction of the crank
itself is such that, by adjustment of the connecting rods, more or
less emulsion may be put upon the plates. Mr. Cowan, however,
intends to adjust the pumps once for all, and to regulate the
amount of emulsion delivered upon the plates by means of driving
wheels of different diameters upon the cranks.

Fig. 10 is a section of the hollow spreading cylinder, made of
sheet silver as thin as paper, so that its weight is light. For
coating large plates it is divided in the center, so as to adapt
itself somewhat to irregularities in the surface of each plate. In
this case it is supported by a third and central thread, as
represented in the cut. Otherwise the cylinder would touch the
center of the plate. Its two halves are held together by a slip of
India rubber.—The Engineer.

THE USE OF AMMONIA AS A REFRIGERATING
AGENT.¹

By Mr. T.B. Lightfoot, M.I.C.E.

Within the last few years considerable progress has been made in
the application of refrigerating processes to industrial purposes,
and the demand for refrigerating apparatus thus created has led to
the production of machines employing various substances as the
refrigerating agent. In a paper read by the author before the
Institution of Mechanical Engineers, in May, 1886, these systems
were shortly described, and general comparisons given as to their
respective merits, scope of application, and cost of working. In
the present paper it is proposed to deal entirely with the use of
ammonia as a refrigerating agent, and to deal with it in a more
full and comprehensive manner than was possible in a paper devoted
to the consideration of a number of different systems and
apparatus. In the United States and in Germany, as well as to some
extent elsewhere, ammonia has been very generally employed for
refrigerating purposes during the last ten years or so. In this
country, however, its application has been extremely limited; and
even at the present time there are but few ammonia machines
successfully at work in Great Britain. No doubt this is, to a large
extent, due to the fact that in the United States and in Germany
there existed certain stimulating causes, both as regards climate
and manufactures, while in this country, on the other hand, these
causes were present only in a modified degree, or were absent
altogether. The consequence was that up to a comparatively recent
date the only machine manufactured on anything like a commercial
scale was the original Harrison’s ether machine, first produced by
Siebe, about the year 1857—a machine which, though answering
its purpose as a refrigerator, was both costly to make and costly
to work. In 1878 the desirability of supplementing our then
existing meat supply by means of the large stocks in our colonies
and abroad led to the rapid development of the special class of
refrigerating apparatus commonly known as the dry air refrigerator,
which, in the first instance, was specially designed for use on
board ship, where it was considered undesirable to employ chemical
refrigerants. Owing to their simplicity, and perhaps also to their
novelty, these cold air machines have very frequently been applied
on land, under circumstances in which the same result could have
been obtained with much greater economy by the use of ammonia or
some other chemical agent. Recently, however, more attention has
been directed to the question of economy, and consideration is now
being given to the applicability of certain machines to certain
special purposes, with the result that ammonia—which is the
agent that, in our present state of knowledge, gives as a rule the
best results for large installations, while on land at any rate its
application for all refrigerating purposes presents no unusual
difficulties—promises to become largely adopted. It is hoped,
therefore, that the following paper respecting its use will be of
interest.

In all cases where a liquid is employed, the refrigerating
action is produced by the change in physical state from the liquid
to the vaporous form. It is, of course, well known that such a
change can only be brought about by the acquirement of heat; and
for the purpose of refrigeration (by which must be understood the
abstraction of heat at temperatures below the normal) it is obvious
that, other things being equal, that liquid is the best which has
the highest heat of vaporization, because with it the least
quantity has to be dealt with in order to produce a given result.
In fact, however, liquids vary, not only in the amount of heat
required to vaporize them (this amount also varying according to
the temperature or pressure at which vaporization occurs), but also
in the conditions under which such change can be effected. For
instance, water has an extremely high latent heat, but as its
boiling point at atmospheric pressure is also high, evaporation at
such temperatures as would enable it to be used for refrigerating
purposes can only be effected under an almost perfect vacuum. The
boiling point of anhydrous ammonia, on the other hand, is
37½° below zero F. at atmospheric pressure, and
therefore for all ordinary cooling purposes its evaporation can
take place at pressures considerably above that of our atmosphere.
Some other agents used for refrigerating purposes are methylic
ether, Pictet’s liquid, sulphur dioxide, and ether. In this
connection it should be stated that Pictet’s liquid is a compound
of carbon dioxide and sulphur dioxide, and is said to possess the
property of having vapor tensions not only much below those of pure
carbon dioxide at equal temperatures, but even below those of pure
sulphur dioxide at temperatures above 78° F. The
considerations, therefore, which chiefly influence the selection of
a liquid refrigerating agent are:

1. The amount of heat required to effect the change from the
liquid to the vaporous state, commonly called the latent heat of
vaporization.

2. The temperatures and pressures at which such change can be
effected.

This latter attribute is of twofold importance; for, in order to
avoid the renewal of the agent, it is necessary to deprive it of
the heat acquired during vaporization, under such conditions as
will cause it to assume the liquid form, and thus become again
available for refrigeration. As this rejection of heat can only
take place if the temperature of the vapor is somewhat above that
of the cooling body which receives the heat, and which, for obvious
reasons, is in all cases water, the liquefying pressure at the
temperature of the cooling water, and the facility with which this
pressure can be reached and maintained, is of great importance in
the practical working of any refrigerating apparatus. Ammonia in
its anhydrous form, the use of which is specially dealt with in
this paper, is a liquid having at atmospheric pressure a latent
heat of vaporization of 900, and a boiling point at the same
pressure of 37½° below zero F. Water being unity, the
specific gravity of the liquid at a temperature of 40° F. is
0.76, and the specific gravity of its vapor is 0.59, air being
unity. In the use of ammonia, two distinct systems are employed. So
far, however, as the mere evaporating or refrigerating part of the
process is concerned, it is the same in both. The object is to
evaporate the liquid anhydrous ammonia at such tension and in such
quantity as will produce the required cooling effect. The actual
tension under which this evaporation should be effected in any
particular case depends entirely upon the temperature at which the
acquirement of heat is to take place, or, in other words, on the
temperature of the material to be cooled. The higher the
temperature, the higher may be the evaporating pressure, and
therefore the higher is the density of the vapor, the greater the
weight of liquid evaporated in a given time, and the greater the
amount of heat abstracted. On the other hand, it must be remembered
that, as in the case of water, the lower the temperature of the
evaporating liquid, the higher is the heat of vaporization. It is
in the method of securing the rejection of heat during condensation
of the vapor that the two systems diverge, and it will be
convenient to consider each of these separately.

The Absorption Process.—The principle employed in
this process is physical rather than mechanical. Ordinary ammonia
liquor of commerce of 0.880 specific gravity, which contains about
38 per cent. by weight of pure ammonia and 62 per cent. of water,
is introduced into a vessel named the generator. This vessel is
heated by means of steam circulating through coils of iron piping,
and a mixed vapor of ammonia and water is driven off. This mixed
vapor is then passed into a second vessel, in order to be subjected
to the cooling action of water. And here, owing to the difference
between the boiling points of water and ammonia, fractional
condensation takes place, the bulk of the water, which condenses
first, being caught and run back to the generator, while the
ammonia in a nearly anhydrous state is condensed and collected in
the lower part of the vessel.

This process of fractional condensation is due to Rees Reece,
and forms an important feature in the modern absorption machine.
Prior to the introduction of this invention, the water evaporated
in the generator was condensed with the ammonia, and interfered
very seriously with the efficiency of the process by reducing the
power of the refrigerating agent by raising its boiling point. In
the improved form of apparatus, ammonia is obtained in a nearly
anhydrous condition, and in this state passes on to the
refrigerator. In this vessel, which is in communication with
another vessel called the absorber, containing cold water or very
weak ammonia liquor, evaporation takes place, owing to the
readiness with which cold water or weak liquor absorbs the ammonia,
water at 59° Fahr. absorbing 727 times its volume of ammonia
vapor. The heat necessary to effect this vaporization is abstracted
from brine or other liquid, which is circulated through the
refrigerator by means of a pump. Owing to the absorption of
ammonia, the weak liquor in the absorber becomes strengthened, and
it is then pumped back into the generating vessel to be again dealt
with as above described.

The absorption apparatus, as applied for cooling purposes,
consists of a generator, which is a vessel of cast iron containing
coils of iron piping to which steam at any convenient pressure is
supplied; an analyzer, in which a portion of the water vapor is
condensed, and from which it flows back immediately into the
generator; a rectifier and condenser, in the upper portion of which
a further condensation of water vapor and a little ammonia takes
place, the liquid thus formed passing back by a pipe to the
analyzer and thence to the generator, while in the lower portion
the ammonia vapor is condensed and collected; and a refrigerator or
cooler, into which the nearly anhydrous liquid obtained in the
condenser is admitted by a pipe and regulating valve, and allowed
to evaporate, the upper portion being in communication with the
absorber.

Through this vessel weak liquor, which has been deprived of its
ammonia in the generator, is continually circulated, after being
first cooled in an economizer by an opposite current of strong cold
liquor passing from the absorber to the generator, while, in
addition, the liquor in the absorber, which would become heated by
the liberation of heat due to the absorption and consequent
liquefaction of the ammonia vapor, is still further cooled by the
circulation of cold water. As the pressure in the absorber is much
lower than that in the generator, the strong liquor has to be
pumped into the latter vessel, and for this purpose pumps are
provided. Though of necessity the various operations have been
described separately, the process is a continuous one, strong
liquor from the absorber being constantly pumped into the generator
through the heater or economizer, while nearly anhydrous liquid
ammonia is being continually formed in the condenser, then
evaporated in the refrigerator and absorbed by the cool weak liquor
passing through the absorber.

Putting aside the effect of losses from radiation, etc., all the
heat expended in the generator will be taken up by the water
passing through the condenser, less that portion due to the
condensation of the water vapor in the analyzer, and plus the
amount due to the difference between the temperature of the liquid
as it enters the generator and the temperature at which it leaves
the condenser. In the refrigerator the liquid ammonia, in becoming
vaporized, will take up the precise quantity of heat that was given
off during its cooling and liquefaction in the condenser, plus the
amount due to the difference in heat of vaporization, owing to the
lower pressure at which the change of state takes place in the
refrigerator, and less the small amount due to the difference in
temperature between the vapor entering the condenser and that
leaving the refrigerator, less also the amount necessary to cool
the liquid ammonia to the refrigerator temperature. When the vapor
enters into solution with the weak liquor in the absorber, the heat
taken up in the refrigerator is imparted to the cooling water,
subject also to corrections for differences of pressure and
temperature. The sources of loss in such an apparatus are:

a. Radiation and conduction of heat from all vessels and
pipes above normal temperature, which can, to a large extent, be
prevented by lagging.

b. Conduction of heat from without into all vessels and
pipes that are below normal temperature, which can also to a large
extent be prevented by lagging.

c. Inefficiency of economizer, by reason of which heat
obtained by the expenditure of steam in the generator is passed on
to the absorber and there uselessly imparted to the cooling
water.

d. The entrance of water into the refrigerator, due to
the liquid being not perfectly anhydrous.

e. The useless evaporation of water in the generator.
With regard to the amount of heat used, it will have been seen that
the whole of that required to vaporize the ammonia, and whatever
water vapor passes off from the generator, has to be supplied from
without. Owing to the fact that the heating takes place by means of
coils, the steam passed through may be condensed, and thus each
pound can be made to give up some 950 units of heat. With the
absorption process worked by an efficient boiler, it may be taken
that 200,000 thermal units per hour may be eliminated by the
consumption of about 100 lb. of coal per hour, with a brine
temperature in the refrigerator of about 20° Fahr.

Compression Process.—In this process ammonia is
used in its anhydrous form. So far as the action of the
refrigerator is concerned, it is precisely the same as it is in the
case of the absorption apparatus, but instead of the vapor being
liquefied by absorption by water, it is drawn from the refrigerator
by a pump, by means of which it is compressed and delivered into
the condenser at such pressure as to cause its liquefaction at the
temperature of the cooling water. It must be borne in mind,
however, that allowance must be made for the rise of temperature of
the water passing through the condenser, and also for the
difference in temperature necessary in order to permit the transfer
of heat from one side of the cooling surface to the other. In a
compression machine the work applied to the pump may be accounted
for as follows:

a. Friction.

b. Heat rejected during compression and discharge.

c. Heat acquired by the ammonia in passing through the
pump.

d. Work expended in discharging the compressed vapor from
the pump.

But against this must be set the useful mechanical work
performed by the vapor entering the pump. The heat rejected in the
condenser is the heat of vaporization taken up in the refrigerator,
less the amount due to the higher pressure at which the change in
physical state occurs, plus the heat acquired in the pump, and less
the amount due to the difference between the temperature at which
the vapor is liquefied in the condenser and that at which it
entered the pump. An ammonia compression machine, as applied to ice
making, contains ice-making tanks, in which is circulated a brine
mixture, uncongealable at any temperature likely to be reached
during the process. This brine also circulates around coils of
wrought iron pipes, in which the liquid ammonia passing from the
condenser is vaporized, the heat required for this vaporization
being obtained from the brine. A pump draws off the ammonia vapor
from the refrigerator coils, and compresses it into the condenser,
where, by means of the combined action of pressure and cooling by
water, it assumes a liquid form, and is ready to be again passed on
to the refrigerator for evaporation. The ammonia compression
process is more economical than the absorption process, and with a
good boiler and engine about 240,000 thermal units per hour can be
eliminated by the expenditure of 100 lb. of coal per hour, with a
brine temperature in the refrigerator of about 20° Fahr.

GENERAL CONSIDERATIONS.

From what has been said, it will have been seen that, so far as
the mere application is concerned, there is no difference whatever
between the absorption and compression processes. The following
considerations, therefore, which chiefly relate to the application
of refrigerating apparatus, will be dealt with quite independent of
either system. The application of refrigerating apparatus may
roughly be divided into the following heads:

a. Ice making.

b. The cooling of liquids.

c. The cooling of stores and rooms.

Ice Making.—For this purpose two methods are
employed, known as the can and cell systems respectively. In the
former, moulds of tinned sheet copper or galvanized steel of the
desired size are filled with the water to be frozen, and suspended
in a tank through which brine cooled to a low temperature in the
refrigerator is circulated. As soon as the water is completely
frozen, the moulds are removed, and dipped for a long time into
warm water, which loosens the blocks of ice and enables them to be
turned out. The thickness of the blocks exercises an important
influence upon the number of moulds required for a given output, as
a block 9 in. thick will take four or five times as long to freeze
solid as one of only 3 in. In the cell system a series of cellular
walls of wrought or cast iron are placed in a tank, the distance
between each pair of walls being from 12 to 16 in., according to
the thickness of the block required. This space is filled with the
water to be frozen. Cold brine circulates through the cells, and
the ice forms on the outer surfaces, gradually increasing in
thickness until the two opposite layers meet and join together. If
thinner blocks are required, the freezing process may be stopped at
any time and the ice removed. In order to detach the ice it is
customary to cut off the supply of cold brine and circulate brine
at a higher temperature through the cells. Ice frozen by either of
the above described methods from ordinary water is more or less
opaque, owing to the air liberated during the freezing process,
little bubbles of which are caught in the ice as it forms, and in
order to produce transparent ice it is necessary that the water
should be agitated during the freezing process in such a way as to
permit the air bubbles to escape. With the can system this is
generally accomplished by means of arms having a vertical or
horizontal movement. These arms are either withdrawn as the ice
forms, leaving the block solid, or they are made to work backward
and forward in the center of the moulds, dividing the block
vertically into two pieces. With the cell system agitation is
generally effected by making a communication between the bottom of
each water space and a chamber below, in which a paddle or wood
piston is caused to reciprocate. The movement thus given to the
water in the chamber is communicated to that in the process of
being frozen, and the small bubbles of air are in this way detached
and set free. The ice which first forms on the sides of the moulds
or cells is, as a rule, sufficiently transparent even without
agitation. The opacity increases toward the center, where the
opposing layers join, and it is, therefore, more necessary to
agitate toward the end of the freezing process than at the
commencement. As the capacity for holding air in solution decreases
if the temperature of the water is raised, less agitation is needed
in hot than in temperate climates. Experiments have been made from
time to time with the view of producing transparent ice from
distilled water, and so dispensing with agitation. In this case the
cost of distilling the water will have to be added to the ordinary
working expenses.

Cooling of Liquids.—In breweries, distilleries,
butter factories, and other places where it is desired to have a
supply of water or brine for cooling and other purposes at a
comparatively low temperature, refrigerating machines may be
advantageously applied. In this case the liquid is passed through
the refrigerator and then utilized in any convenient manner.

Cooling of Rooms.—For this purpose the usual plan
is to employ a circulation of cold brine through rows of iron
piping, placed either on the ceiling or on the walls of the rooms
to be cooled. In this, as in the other cases where brine is used,
it is employed merely as a medium for taking up heat at one place
and transferring it to the ammonia in the refrigerator, the ammonia
in turn completing the operation by giving up the heat to the
cooling water during liquefaction in the condenser. The brine pipes
cool the adjacent air, which, in consequence of its greater
specific gravity, descends, being replaced by warmer air, which in
turn becomes cold, and so the process goes on. Assuming the air to
be sufficiently saturated, which is generally the case, some of the
moisture in it is condensed and frozen on the surface of the pipes;
and if the air is renewed in whole or in part from the outside, or
if the contents of the chamber are wet, the deposit of ice in the
pipes will in time become so thick as to necessitate its being
thawed off. This is accomplished by turning a current of warm brine
through the pipes. Another method has been proposed, in which the
brine pipes are placed in a separate compartment, air being
circulated through this compartment to the rooms, and back again to
the cooling pipes in a closed cycle by means of a fan. This plan
was tried on a large scale by Mr. Chambers at the Victoria Docks,
but for some reason or other was abandoned. One difficulty is the
collection of ice from the moisture deposited from the air, which
clogs up the spaces between the pipes, besides diminishing their
cooling power. This, in some cases, can be partially obviated by
using the same air over again, but in most instances special means
would have to be provided for frequent thawing off, the pipes
having, on account of economy of space and convenience, to be
placed so close together, and to be so confined in surface, that
they are much more liable to have their action interfered with than
when placed on the roof or walls of the room.

In addition to the foregoing there are, of course, many other
applications of ammonia refrigerating machines of a more or less
special nature, of which time will not permit even a passing
reference. Many of these are embraced in the second class, cold
water or brine being used for the cooling of candles, the
separation of paraffin, the crystallization of salts, and for many
other purposes. In the same way cold brine has been used with great
success for freezing quicksand in the sinking of shafts, the
excavation being carried out and the watertight tubing or lining
put in while the material is in a solid state. In a paper such as
this it would be quite impracticable to enter into details of
construction, and the author has therefore confined himself chiefly
to principles of working. In conclusion, however, it may be added
that in ammonia machines, whether on the absorption or compression
systems, no copper or alloy of copper can be used in parts
subjected to the action of the ammonia. Cast or wrought iron and
steel may, however, be used, provided the quality is good, but
special care must be taken in the construction of those parts of
absorption machines which are subjected to a high temperature. In
both classes of apparatus first-class materials and workmanship are
most absolute essentials.

[Continued from Supplement, No. 646,
p. 10319.]

ELEMENTS OF ARCHITECTURAL DESIGN.¹

By H. H. Statham.

III.—CONTINUED.

The Romans, in their arched constructions, habitually
strengthened the point against which the vault thrust by adding
columnar features to the walls, as shown in Fig. 108; thus again
making a false use of the column in a way in which it was never
contemplated by those who originally developed its form. In
Romanesque architecture the column was no longer used for this
purpose; its place was taken by a flat pilaster-like projection of
the wall (plan and section, Fig. 109), which gave sufficient
strength for the not very ambitious vaulted roofs of this period,
where often in fact only the aisles were vaulted, and the center
compartment covered with a wooden roof. At first this pilaster-like
form bore a reminiscence of a classic capital as its termination; a
moulded capping under the eaves of the building. Next this capping
was almost insensibly dropped, and the buttress became a mere flat
strip of wall. As the vaulting became bolder and more ambitious,
the buttress had to be made more massive and of greater projection,
to afford sufficient abutment to the vault, more especially toward
the lower part, where the thrust of the roof is carried to the
ground. Hence arose the tendency to increase the projection of the
buttress gradually downward, and this was done by successive slopes
or “set-offs,” as they are termed, which assisted (whether
intentionally or not in the first instance) in further aiding the
correct architectural expression of the buttress. Then the vaulting
of the center aisle was carried so high and treated in so bold a
manner, with a progressive diminution of the wall piers (as the
taste for large traceried windows developed more and more), that a
flying buttress (see section, Fig. 110) was necessary to take the
thrust across to the exterior buttresses, and these again, under
this additional stress, were further increased in projection, and
were at the same time made narrower (to allow for all the window
space that was wanted between them), until the result was that the
masses of wall, which in the Romanesque building were placed
longitudinally and parallel to the axis of the building, have all
turned about (Fig. 110, plan) and placed themselves with their
edges to the building to resist the thrust of the roofing. The same
amount of wall is there as in the Romanesque building, but it is
arranged in quite a new manner, in order to meet the new
constructive conditions of the complete Gothic building.

Figs. 108-114.

It will be seen thus how completely this important and
characteristic feature of Gothic architecture, the buttress, is the
outcome of practical conditions of construction. It is treated
decoratively, but it is itself a necessary engineering expedient in
the construction. The application of the same principle, and its
effect upon architectural expression, may be seen in some other
examples besides that of the buttress in its usual shape and
position. The whole arrangement and disposition of an arched
building is affected by the necessity of providing counterforts to
resist the thrust of arches. The position of the central tower, for
instance, in so many cathedrals and churches, at the intersection
of the nave and transepts, is not only the result of a feeling for
architectural effect and the centralizing of the composition, it is
the position in which also the tower has the cross walls of nave
and transepts abutting against it in all four directions: if the
tower is to be placed over the central roof at all, it could only
be over this point of the plan. In the Norman buildings, which in
some respects were finer constructions than those of later Gothic,
the desire to provide a firm abutment for the arches carrying the
tower had a most marked effect on the architectural expression of
the interior. At Tewkesbury, for instance, while the lower piers
are designed in the usual way toward the north and south sides
(viz., as portions of a pier of nearly square proportion standing
under the angle of the tower), in the east and west direction the
tower piers run out into great solid masses of wall, in order to
insure a sufficient abutment for the tower arches. On the north and
south sides the solid transept walls were available immediately on
the other side of the low arch of the side aisle, but on the east
and west sides there were only the nave and choir arcades to take
the thrust of the north and south tower arches, and so the Normans
took care to interpose a massive piece of wall between, in order
that the thrust of the tower arches might be neutralized before it
could operate against the less solid arcaded portions of the walls.
This expedient, this great mass of wall introduced solely for
constructive reasons, adds greatly to the grandeur of the interior
architectural effect. The true constructive and architectural
perception of the Normans in this treatment of the lower piers is
illustrated by the curious contrast presented at Salisbury. There
the tower piers are rather small, the style is later, and the
massive building of the Normans had given way to a more graceful
but less monumental manner of building. Still the abutment of the
tower arches was probably sufficient for the weight of the tower as
at first built; but when the lofty spire was put on the top of
this, its vertical weight, pressing upon the tower arches and
increasing their horizontal thrust, actually thrust the nave and
choir arcades out of the perpendicular toward the west and east
respectively, and there they are leaning at a very perceptible
angle away from the center of the church—the architectural
expression, in a very significant form, of the neglect of balance
of mass in construction.

But while the buttress in Gothic architecture has been in
process of development, what has the vault been doing? We left it
(Fig. 92) in the condition of a round wagon vault, intersected by
another similar vault at right angles. By that method of treatment
we got rid of the continuous thrust on the walls. But there were
many difficulties to be faced in the construction of vaulting after
this first step had been taken, difficulties which arose chiefly
from the rigid and unmanageable proportions of the circular arch,
and which could not be even partially solved till the introduction
of the pointed arch. The pointed arch is the other most marked and
characteristic feature of Gothic architecture, and, like the
buttress, it will be seen that it arose entirely out of
constructive difficulties.

These difficulties were of two kinds; the first arose from the
tendency of the round arch, when on a large scale and heavily
weighted, to sink at the crown if there is even any very slight
settlement of the abutments. If we turn again to diagram 77, and
observe the nearly vertical line formed there by the joints of the
keystone, and if we suppose the scale of that arch very much
increased without increasing the width of each voussoir, and
suppose it built in two or three rings one over the other (which is
really the constructive method of a Gothic arch), we shall see that
these joints in the uppermost portion of the arch must in that case
become still more nearly vertical; in other words, the voussoirs
almost lose the wedge shape which is necessary to keep them in
their places, and a very slight movement or settlement of the
abutments is sufficient to make the arch stones lose some of their
grip on each other and sink more or less, leaving the arch flat at
the crown. There can be no doubt that it was the observance of this
partial failure of the round arch (partly owing probably to their
own careless way of preparing the foundations for their
piers—for the mediæval builders were very bad engineers
in that respect) which induced the builders of the early
transitional abbeys, such as Furness and Fountains and Kirkstall,
to build the large arches of the nave pointed, though they still
retain the circular-headed form for the smaller arches in the same
buildings, which were not so constructively important. This is one
of the constructive reasons which led to the adoption of the
pointed arch in mediæval architecture, and one which is
easily stated and easily understood. The other influence is one
arising out of the lengthened conflict with the practical
difficulties of vaulting, and is a rather more complicated matter,
which we must now endeavor to follow out.

Figs. 93-107.

Looking at Fig. 92, it will be seen that in addition to the
perspective sketch of the intersecting arches, there is drawn under
it a plan, which represents the four points of the abutment of the
arches (identified in plan and perspective sketch as A, B, C, D),
and the lines which are taken by the various arches shown by dotted
lines. Looking at the perspective sketch, it will be apparent that
the intersection of the two cross vaults produces two intersecting
arches, the upper line of which is shown in the perspective sketch
(marked e and f); underneath, this intersection of the two arches,
which forms a furrow in the upper side of the construction, forms
an edge which traverses the space occupied by the plan of the
vaulting as two oblique arches, running from A to C and from B to D
on the plan. Although these are only lines formed by the
intersection of two cross arches, still they make decided arches to
the eye, and form prominent lines in the system of vaulting; and in
a later period of vaulting they were treated as prominent lines and
strongly emphasized by mouldings; but in the Roman and early
Romanesque vaults they were simply left as edges, the eye being
directed rather to the vaulting surfaces than to the edges. The
importance of this distinction between the vaulting surfaces and
their meeting edges or groins² will be
seen just now. The edges, nevertheless, as was observed, do form
arches, and we have therefore a system of cross arches (A B and C
D³ Fig. 95), two wall arches (A, D and
B C), and two oblique arches (A C and B D), which divide the space
into four equal triangular portions; this kind of vaulting being
hence called quadripartite vaulting. In this and the other
diagrams of arches on this page, the cross arches are all shown in
positive lines, and the oblique arches in dotted lines.

We have here a system in which four semicircular arches of the
width of A B are combined with two oblique arches of the width of A
C, springing from the same level and supposed to rise to the same
height. But if we draw out the lines of these two arches in a
comparative elevation, so as to compare their curves together, we
at once find we are in a difficulty. The intersection of the two
circular arches produces an ellipse with a very flat crown, and
very liable to fail. If we attempt to make the oblique arch a
segment only of a large circle, as in the dotted line at 94, so as
to keep it the same level as the other without being so flat at the
top, the crown of the arch is safer, but this can only be done at
the cost of getting a queer twist in the line of the oblique arch,
as shown at D, Fig. 93. The like result of a twist of the line of
the oblique arch would occur if the two sides of the space we are
vaulting over were of different lengths, i.e., if the
vaulting space were otherwise than a square, as long as we are
using circular arches. If we attempt to make the oblique arches
complete circles, as at Fig. 96, we see that they must necessarily
rise higher than the cross and side arches, so that the roof would
be in a succession of domical forms, as at Fig. 97. There is the
further expedient of “stilting” the cross arches, that is, making
the real arch spring from a point above the impost and building the
lower portion of it vertical, as shown in Fig. 98. This device of
stilting the smaller arches to raise their crowns to the level of
those of the larger arches was in constant use in Byzantine and
early Romanesque architecture, in the kind of manner shown in the
sketch, Fig. 99; and a very clumsy and makeshift method of dealing
with the problem it is; but something of the kind was inevitable as
long as nothing but the round arch was available for covering
contiguous spaces of different widths. The whole of these
difficulties were approximately got over in theory, and almost
entirely in practice, by the adoption of the pointed arch. By its
means, as will be seen in Fig. 100, arches over spaces of different
widths could be carried to the same height, yet with little
difference in their curves at the springing, and without the
necessity of employing a dangerously flat elliptical form in the
oblique arch. A sketch of the Gothic vault in this form, and as the
intersection of the surfaces of pointed vaults, is shown in Fig.
101.

But now another and most important change was to come over the
vault. The mediæval architects were not satisfied with the
mere edge left by the Romans in their vaults, and even before the
full Gothic period the Roman builders had emphasized their oblique
arches in many cases by ponderous courses of moulded or unmoulded
stone in the form of vaulting ribs. These, in the case of Norman
building, were probably not merely put for the purpose of
architectural expression, but also because they afforded an
opportunity of concealing behind the lines of a regularly curved
groin rib the irregular curves which were really formed by the
junction of the vaulting surfaces. But when the vault become more
manageable in its curves after the adoption of the pointed arch,
the groin rib became adopted in the early pointed vaulting as a
means of giving expression and carrying up the lines of the
architectural design. On its edge were stones moulded with the deep
undercut hollows of early English moulding, defining the curves of
the oblique as well as of the cross arches with strongly marked
lines, and, moreover, falling on a level with each other in
architectural importance; the oblique vault of the arch is no
longer a secondary line in the vaulting design; on the contrary,
the cross arches are usually omitted, as shown in Figs. 102 and 103
(view and plan of an early Gothic quadripartite vault); so that the
cross rib, which, in the early Romanesque wagon vault (Fig. 90),
was the one marked line on the vaulting surface, has now been
obliterated, and the line of the oblique arch (E F, Figs. 102, 103)
has taken its place.

The effect of the strongly marked lines of the groin ribs,
radiating from the cap of the shaft which was their architectural
support, seems to have been so far attractive to the mediæval
builders that they soon endeavored to improve upon it and carry it
further by multiplying the groin ribs. One of the stages of this
progress is shown in Figs. 104, 105. Here it will be seen that the
cross rib is again shown, and that intermediate ribs have been
introduced between it and the oblique rib. The richness of effect
of the vault is much heightened thereby; but a very important
modification in the mode of constructing it has been introduced. As
the groin ribs become multiplied, it came to be seen that it was
easier to construct them first, and fill in the spaces afterward;
accordingly the groin, instead of being, as it was in the early
days of vaulting, merely the line formed by the meeting of two arch
surfaces, became a kind of stone scaffolding or frame work, between
which the vaulting surfaces were filled in with lighter material.
This arrangement of course made an immense difference in the whole
principle of constructing the vault, and rendered it much more
ductile in the hands of the builder, more capable of taking any
form which he wished to impose on it, than when the vault was
regarded and built as an intersection of surfaces. There was still
one difficulty, however, one slight failure both practical and
theoretical in the vault architecture, which for a long time much
exercised the minds of the builders. The ribs of the vaulting being
all of unequal length, they had to assume different curves almost
immediately on rising from the impost; and as the mouldings of the
ribs have to be run into each other (“mitered” is the technical
term) on the impost, there not being room to receive them all
separately, it was almost impossible to get them to make their
divergence from each other in a completely symmetrical manner; the
shorter ribs with the quicker curves parted from each other at a
lower point than the larger ones, and the “miters” occurred at
unequal heights. The effort to get over this unsatisfactory and
irregular junction of the ribs at the springing was made first by
setting back the feet of the shorter ribs on the impost capping,
somewhat in the rear of the feet of the larger ribs, so as to throw
their parting point higher up; but this also was only a makeshift,
which it was hoped the eye would pass over; and in fact it is
rarely noticeable except to those who know about it and look for
it. Still the defect was there, and was not got over until the idea
occurred of making all the ribs of the same curvature and the same
length, and intercepting them all by a circle at the apex of the
vault, as shown in Figs. 106, 107; the space between the circles at
the apex of the vault being practically a nearly flat surface or
plafond held in its place by the arches surrounding it;
though, for effect, it is often treated otherwise in external
appearance, being decorated by pendants giving a reversed curve at
this point, but which of course are only ornamental features hung
from the roof. If we look again at Fig. 104, we shall see that this
was a very natural transition after all, for the arrangement of the
ribs and vaulting surfaces in that example is manifestly suggestive
of a form radiating round the central point of springing, though it
only suggests that, and does not completely realize it. But here
came a further and very curious change in the method of building
the vault, for as the ribs were made more numerous, for richness of
effect, in this form of vaulting, it was discovered that it was
much easier to build the whole as a solid face of masonry, working
the ribs on the face of it. Thus the ribs, which in the
intermediate period were the constructive framework of the vault,
in the final form of fan vaulting came back to their original use
as merely a form of architectural expression, meant to carry on the
architectural lines of the design; and they perform, on a larger
scale and with a different expression, much the same kind of
function which the fluting lines performed in the Greek column. The
fan vault is therefore a kind of inverted dome, built up in courses
on much the same principle as a dome, but a convex curve
internally, instead of a concave one, the whole forming a series of
inverted conoid forms abutting against the wall at the foot and
against each other at their upper margins. This form of roof is
wonderfully rich in effect, and has the appearance of being a piece
of purely artistic work done for the pleasure of seeing it; yet, as
we have seen, it is in reality, like almost everything good in
architecture, the logical outcome of a contention with structural
problems.

We have already noticed the suggestion, in early Gothic or
Romanesque, of the dividing up of a pier into a multiple pier, of
which each part supports a special member of the superstructure, as
indicated in Fig. 90. The Gothic pier, in its development in this
respect, affords a striking example of that influence of the
superstructure on the plan which has before been referred to. The
peculiar manner of building the arch in Gothic work led almost
inevitably to this breaking up of the pier into various members.
The Roman arch was on its lower surface a simple flat section, the
decorative treatment in the way of mouldings being round the
circumference, and not on the under side or soffit of the
arch, and in early Romanesque work this method was still followed.
The mediæval builders, partly in the first instance because
they built with smaller stones, adopted at an early period the plan
of building an arch in two or more courses or rings, one below and
recessed within the other. As the process of moulding the arch
stones became more elaborated, and a larger number of subarches one
within another were introduced, this characteristic form of
subarches became almost lost to the eye in the multiplicity of the
mouldings used. But up to nearly the latest period of Gothic
architecture this form may still be traced, if looked for, as the
basis of the arrangement of the mouldings, which are all formed by
cutting out of so many square sections, recessed one within the
other. This will be more fully described in the next lecture. We
are now speaking more especially of the pier as affected by this
method of building the arches in recessed orders. If we consider
the effect of bringing down on the top of a square capital an arch
composed of two rings of squared stones, the lower one only half
the width (say) of the upper one, it will be apparent that on the
square capital the arch stones would leave a portion of the capital
at each angle bare, and supporting nothing.⁴ This looks
awkward and illogical, and accordingly the pier is modified so as
to suit the shape of the arch. Figs. 111, 112, 113, and 114, with
the plans, B C D, accompanying them, illustrate this development of
the pier. Fig. 111 is a simple cylindrical pier with a coarsely
formed capital, a kind of reminiscence of the Doric capital, with a
plain Romanesque arch starting from it. Fig. 112, shown in plan at
B, is the kind of form (varied in different examples) which the
pier assumed in Norman and early French work, when the arch had
been divided into two recessed orders. The double lines of the arch
are seen springing from the cap each way, in the elevation of the
pier. If we look at the plan of the pier, we see that, in place of
the single cylinder, it is now a square with four smaller half
cylinders, one on each face. Of these, those on the right and left
of the plan support the subarches of the arcade; the one on the
lower side, which we will suppose to be looking toward the nave,
supports the shaft which carries the nave vaulting, and which
stands on the main capital with a small base of its own, as seen in
Fig. 112—a common feature in early work; and the half column
on the upper side of the plan supports the vaulting rib of the
aisle. In Fig. 113 and plan C, which represents a pier of nearly a
century later, we see that the pier is broken up by perfectly
detached shafts, each with its own capital, and each carrying a
group of arch mouldings, which latter have become more elaborated.
Fig. 114 and plan D show a late Gothic fourteenth century pier, in
which the separate shafts have been abandoned, or rather absorbed
into the body of the pier, and the pier is formed of a number of
moulded projections, with hollows giving deep shadows between them,
and the capitals of the various members run into one another,
forming a complete cap round the pier. This pier shows a remarkable
contrast in every way to B, yet it is a direct development from the
latter. In this late form of pier, it will be observed that the
projection, E, which carries the vaulting ribs of the nave, instead
of springing from the capital, as in the early example, Fig. 111,
springs from the floor, and runs right up past the capital; thus
the plan of the vaulting is brought, as it were, down on to the
floor, and the connection between the roofing of its building and
its plan is as complete as can well be. In Fig. 113 the vaulting
shaft is supposed to stop short of the capital and to spring from a
corbel in the wall, situated above the limit of the drawing. This
was a common arrangement in the “Early English” and “Early
Decorated” periods of Gothic, but it is not so logical and
complete, or so satisfactory either to the eye or to the judgment,
as starting the vaulting shaft from the floor line. The connection
between the roofing and the plan may be further seen by looking at
the portion of a mediæval plan given under Fig. 110, where
the dotted lines represent the course of the groin ribs of the roof
above. It will be seen how completely these depend upon the plan,
so that it is necessary to determine how the roof in a vaulted
building is to be arranged before setting out the ground plan.

Thus we see that the Gothic cathedral, entirely different in its
form from that of the Greek temple, illustrates, perhaps, even more
completely than the Greek style, the same principle of correct and
truthful expression of the construction of the building, and that
all the main features which give to the style its most striking and
picturesque effects are not arbitrarily adopted forms, but are the
result of a continuous architectural development based on the
development of the construction. The decorative details of the
Gothic style, though differing exceedingly from those of the Greek,
are, like the latter, conventional adaptations of suggestions from
nature; and in this respect again, as well as in the character of
the mouldings, we find both sides illustrating the same general
principle in the design of ornament, in its relation to position,
climate, and material; but this part of the subject will be more
fully treated of in the next lecture.

We have now arrived at a style of architectural construction and
expression which seems so different from that of Greek
architecture, which we considered in the last lecture, that it is
difficult to realize at first that the one is, in regard to some of
its most important features, a lineal descendant of the other. Yet
this is unquestionably the case. The long thin shaft of Gothic
architecture is descended, through a long series of modifications,
from the single cylindrical column of the Greek; and the carved
mediæval capital, again, is to be traced back to the Greek
Corinthian capital, through examples in early French architecture,
of which a tolerably complete series of modifications could be
collected, showing the gradual change from the first deviations of
the early Gothic capital from its classical model, while it still
retained the square abacus and the scroll under the angle and the
symmetrical disposition of the leaves, down to the free and
unconstrained treatment of the later Gothic capital. Yet with these
decided relations in derivation, what a difference in the two
manners of building! The Greek building is comparatively small in
scale, symmetrical and balanced in its main design, highly finished
in its details in accordance with a preconceived theory. The Gothic
building is much more extensive in scale, is not necessarily
symmetrical in its main design, and the decorative details appear
as if worked according to the individual taste and pleasure of each
carver, and not upon any preconceived theory of form or proportion.
In the Greek building all the predominant lines are horizontal; in
the mediæval building they are vertical. In the Greek
building every opening is covered by a lintel; in the Gothic
building every opening is covered by an arch. No two styles, it
might be said, could be more strongly contrasted in their general
characteristics and appearance. Yet this very contrast only serves
to emphasize the more strongly the main point which I have been
wishing to keep prominent in these lectures—that
architectural design, rightly considered, is based on and is the
expression of plan and construction. In Greek columnar architecture
the salient feature of the style is the support of a cross lintel
by a vertical pillar; and the main effort of the architectural
designer is concentrated on developing the expression of the
functions of these two essential portions of the structure. The
whole of the openings being bridged by horizontal lintels, the
whole of the main lines of the superstructure are horizontal, and
their horizontal status is as strongly marked as possible by the
terminating lines of the cornice—the whole of the pressures
of the superstructure are simply vertical, and the whole of the
lines of design of the supports are laid out so as to emphasize the
idea of resistance to vertical pressure. The Greek column, too, has
only one simple office to perform, that of supporting a single mass
of the superstructure, exercising a single pressure in the same
direction. In the Gothic building the main pressures are oblique
and not vertical, and the main feature of the exterior
substructure, the buttress, is designed to express resistance to an
oblique pressure; and no real progress was made with the
development of the arched style until the false use of the apparent
column or pilaster as a buttress was got rid of, and the true
buttress form evolved. On the interior piers of the arcade there is
a resolution of pressures which practically results in a vertical
pressure, and the pier remains vertical; but the pressure upon it
being the resultant of a complex collection of pressures, each of
these has, in complete Gothic, its own apparent vertical supporting
feature, so that the plan of the substructure becomes a logical
representation of the main features and pressures of the
superstructure. The main tendency of the pointed arched building is
toward vertically, and this vertical tendency is strongly
emphasized and assisted by the breaking up of the really solid mass
of the pier into a number of slender shafts, which, by their
strongly marked parallel lines, lead the eye upward toward the
closing-in lines of the arcade and of the vaulted roof which forms
the culmination of the whole. The Greek column is also assisted in
its vertical expression by the lines of the fluting; but as the
object of these is only to emphasize the one office of the one
column, they are strictly subordinate to the main form, are in fact
merely a kind of decorative treatment of it in accordance with its
function. In the Gothic pier the object is to express complexity of
function, and the pier, instead of being a single fluted column, is
broken up into a variety of connected columnar forms, each
expressive of its own function in the design. It may be observed
also that the Gothic building, like the Greek, falls into certain
main divisions arising out of the practical conditions of its
construction, and which form a kind of “order” analogous to the
classic order in a sense, though not governed by such strict
conventional rules. The classic order has its columnar support, its
beam, its frieze for decorative treatment. The Gothic order has its
columnar support, its arch (in place of the beam), its decoratively
treated stage (the triforium), occupying the space against which
the aisle roof abuts, and its clerestory, or window stage. All
these arise as naturally out of the conditions and historical
development of the structure in the Gothic case as in the Greek
one, but the Greek order is an external, the Gothic an internal
one. The two styles are based on constructive conditions totally
different the one from the other; their expression and character
are totally different. But this very difference is the most
emphatic declaration of the same principle, that architectural
design is the logical, but decorative, expression of plan and
construction.

THE METEOROLOGICAL STATION ON MT. SANTIS.

THE METEOROLOGICAL STATION ON MT. SANTIS.

At the second International Meteorological Congress, in 1879,
the erection of an observatory on the top of a high mountain was
considered. The Swiss Meteorological Commission undertook to carry
out the project, and sent out circulars to different associations,
governments, and private individuals requesting single or yearly
contributions to aid in defraying the expense of the station. In
December, 1881, an extra credit of about $1,000 was granted by the
Bundesversammlung for the initial work on the station, which was
temporarily placed in the Santis Hotel, and a telegraph was put up
between that place and Weisbad in August, 1882, so that on
September 1 of the same year the meteorological observations were
begun.

At the end of August, 1885, this temporary arrangement expired,
and the enterprise could not be carried on unless the support of
the same was undertaken by the Union. On March 27, 1885, the
Bundesversammlung decided to take the necessary steps. Mr. Fritz
Brunner, who died May 1, 1885, left a large legacy for the
enterprise, making it possible to build a special observatory.

For this purpose the northeast corner of the highest rocky peak
was blasted out and the building was so placed that the wall of
rock at the rear formed an excellent protection from the high west
winds. By the first of October, last year, the building was ready
for occupancy, and there was a quiet opening at which Mr. Potch,
director of the Blue Hill Observatory, near Boston, and others were
present.

The building is 26 feet long, 19 feet deep, and 30 feet high,
and is very solid and massive, having been built of the limestone
blasted from the rock. It consists of a ground floor containing the
telegraph office, the observers’ work room, and the kitchen and
store rooms; the first story, in which are the living and sleeping
rooms for the observers and their assistants; and the second story,
living and sleeping rooms for visiting scientists who come to make
special observations, and a reserve room. The barometer and
barograph are placed in the second story, at a height of about
8,202 feet above the level of the sea, whereas in the hotel they
were only about 8,093 feet above the sea level. The flat roof, of
wood and cement, which extends very little above the plateau of the
mountain top, is admirably adapted for making observations in the
open air. All the rooms in the house are ceiled with wood, and the
walls and floors of the ground floor and first story and the
ceilings of the second story are covered with insulating material.
The cost of the building, including the equipments, amounted to
about $11,200.

The fact that since the erection of the Santis station there has
been a still higher station constructed on Sonnblick (10,137 feet
high) does not decrease the value of the former, for the greater
the number of such elevated stations, the better will be the
meteorological investigations of the upper air currents. The
present observer at Santis is Mr. C. Saxer, who has endured the
hardships and privations of a long winter at the station.

The anemometer house, which is shown in our illustration, is
connected with the main house by a tunnel. Several times during the
day records are taken of the barometer, the thermometer, the
weather vane, as well as notes in regard to the condition of the
weather, the clouds, fall of rain or snow, etc. A registering
aneroid barometer marks the pressure of the atmosphere hourly, and
two turning thermometers register the temperature at midnight and
at four o’clock in the morning.—Illustrirte
Zeitung.

THE CARE OF THE EYES.¹

By Prof. David Webster, M.D.

“The light of the body is the eye.” Of all our senses, sight,
hearing, touch, taste, and smell, the sight is that which seems to
us the most important. Through the eye, the organ of vision, we
gain more information and experience more pleasure, perhaps, than
through any or all our other organs of sense. Indeed, we are apt to
depreciate the value of our other senses when comparing them to the
eyesight. It is not uncommon to hear a person say, “I would rather
die than be blind.” But no one says, “I would rather die than lose
my hearing.” As a matter of fact, the person who is totally blind
generally appears to be more cheerful, happier, than one who is
totally deaf. Deaf mutes are often dull, morose, quick tempered,
obstinate, self-willed, and difficult to get along with, while the
blind are not infrequently distinguished for qualities quite the
reverse. It is worthy of remark that the eye is that organ of sense
which is most ornamental as well as useful, and the deprivation of
which constitutes the most visible deformity. But it is unnecessary
to enter into a comparison of the relative value of our senses or
the relative misfortune of our loss of any one of them. We need
them all in our daily struggle for existence, and it is necessary
to our physical and mental well-being, as well as to our success in
life, that we preserve them all in as high a degree of perfection
as possible. We must not lose sight of the fact that all our organs
of sense are parts of one body, and that whatever we do to improve
or preserve the health of our eyes cannot do harm to any other
organ. We shall be able to “take care of our eyes” more
intelligently if we know something of their structure and how they
perform their functions. The eye is a hollow globe filled with
transparent material and set in a bony cavity of the skull, which,
with the eyelids and eyelashes, protect it from injury. It is moved
at will in every direction by six muscles which are attached to its
surface, and is lubricated and kept moist by the secretions of the
tear gland and other glands, which secretions, having done their
work, are carried down into the nose by a passage especially made
for the purpose—the tear duct. We are all familiar with the
fact that our eyes are “to see with,” but in order to be able to
take care of our eyes intelligently, it is necessary to understand
as far as possible how to see with them.

THE BACK WALL OF THE EYE.

It is a remarkable fact that every object we see has its picture
formed upon the back wall of our eyes. The eye is a darkened
chamber, and the whole of the front part of it acts as a lens to
bring the rays of light coming from objects we wish to see to a
focus on its back wall, thus forming a picture there as distinct as
the picture formed in the camera obscura of the photographer. This
has not only been proved by the laws of optics, but has been
actually demonstrated in the eyes of rabbits and other animals.
Experimenters have held an object before the eye of a rabbit for a
few moments, and have then killed the animal and removed the eye as
quickly as possible, and laid its back wall bare, and have
distinctly seen there the picture of the object upon which the eye
had been fixed. It is a truly wonderful fact that these pictures
upon the back wall of the eye can be changed so rapidly that the
picture of the object last looked at disappears in an instant and
makes way for the picture of the next. We know that the picture
formed on the back wall of the eye is carried back to the brain by
the optic nerve, but there our knowledge stops. Science cannot tell
us how the brain, and through it the mind, completes the act of
seeing. It is there that the finite and the infinite touch, and, as
our minds are finite, we cannot comprehend the infinite.

But there is enough that we can understand, and it shall be my
endeavor in this paper to make some plain statements that will help
as a guide in the preservation of those wonderful and useful
organs.

FAR AND NEAR SIGHTEDNESS.

We have to use our eyes for near and far distant vision. In
gathering pictures of distant objects the normally shaped eye puts
forth little or no effort. It is the near work, such as reading,
sewing, or drawing, that puts a real muscular strain upon the eyes.
There are certain rules that apply to the use of the eyes for such
near work regardless of the age of the person.

READING.

1. In reading, a book or newspaper should be held at a distance
of from ten to fifteen inches from the eyes. It is hardly necessary
to caution anybody not to hold the print further away than fifteen
inches. The only objection to holding ordinary print too far away
is that in so doing the pictures formed on the back wall of the eye
are too small to be readily and easily perceived, and the close
attention consequently necessary causes both the eyes and the brain
to tire. Most persons quickly find this out themselves, and the
tendency is rather to hold the book too near, for the nearer the
object to the eye, the larger its picture upon the retina, or back
eye wall. But here we encounter another danger. The nearer the
object the eyes are concentrated upon, the greater the muscular
effort necessary; so that by holding the book too near, the labor
of reading is greatly increased, and the long persistence in such a
habit is likely to produce weak eyes, and may, in some instances,
lead to real near-sightedness. When children are observed to have
acquired this habit and cannot be persuaded out of it, they should
always be taken to a physician skilled in the treatment of the eye
for examination and advice. A little attention at such a time may
save them from a whole lifetime of trouble with their eyes. Of
course, the larger the print, the farther it may be held from the
eyes.

POSITION.

2. The position of the person with regard to the light should be
so that the latter will fall upon the page he is reading, and not
upon his eyes. It is generally considered most convenient to have
the light shine over the left shoulder, so that in turning the
leaves of the book, the shadow of the hand upon the page is
avoided. It is not always possible to do this, however, and, at the
same time, to get plenty of light upon the page. When one finds
himself compelled to face the light in reading, or in standing at a
desk bookkeeping, he should always contrive to shade his eyes from
a direct light. This may be done with a large eye shade projecting
from the brow. A friend of mine, a physician, is very fond of
reading by a kerosene lamp, the lamp being placed on a table by his
side, and the direct light kept from his eyes by means of a piece
of cardboard stuck up by the lamp chimney.

PROPER LIGHT.

3. The illumination should always be sufficient. Nothing is more
injurious to the eyes than reading by a poor light. Many persons
strain their eyes by reading on into the twilight as long as they
possibly can. They become interested and do not like to leave off.
Some read in the evening at too great a distance from the source of
light, forgetting that the quantity of light diminishes as the
square of the distance from the source of light increases. Thus, at
four feet, one gets only one-sixteenth part of the light upon his
page that he would at one foot. It is the duty of parents and
others who have charge of children to see to it that they do not
injure their eyes by reading by insufficient light, either daylight
or artificial light. There is a common notion that electric light
is bad for the eyes. The only foundation I can think of for such a
notion is that it is trying to the eyes to gaze directly at the
bright electric light. It is bad to gaze long at any source of
light, and the brighter the source of light gazed at, the worse for
the eyes, the sun being the worst of all. I have seen more than one
person whose eyes were permanently injured by gazing at the sun,
during an eclipse or otherwise. As a matter of fact, nothing short
of sunlight is better than the incandescent electric light to read
by or to work by.

READING IN BED.

As to reading while lying down in bed or on a lounge, I can see
no objection to it so far as the eyes are concerned, provided the
book is held in such a position that the eyes do not have to be
rolled down too far. Unless the head is raised very high by
pillows, however, it will be found very fatiguing to hold the book
high enough, not to mention the danger of falling asleep, and of
upsetting the lamp or candle, and thus setting the bed on fire.
Many persons permanently weaken their eyes by reading to pass away
the tedious hours during recovery from severe illness. The muscles
of the eyes partake of the general weakness and are easily
overtaxed. Persons in this condition may be read to, but should
avoid the active use of their own eyes.

READING IN RAIL CARS.

Reading while in the rail cars or in omnibuses is to be avoided.
The rapid shaking, trembling or oscillating motion of the cars
makes it very difficult to keep the eyes fixed upon the words, and
is very tiresome. I have seen many persons who attributed the
failure of their eyes to the daily habit of reading while riding to
and from the city. Children should be cautioned against reading
with the head inclined forward. The stooping position encourages a
rush of blood to the head, and consequently the eyes become
congested, and the foundations for near-sightedness are laid.

(To be continued.)

TESTING INDIGO DYES.

The author deals with the question whether a sample of goods is
dyed with indigo alone or with a mixture of indigo and other blue
coloring matters. His method may be summarized as follows: Threads
of the material in question should give up no coloring matter to
boiling water. Alcohol at 50 and at 95 per cent. (by volume) ought
to extract no color, even if gently warmed (not boiled). Solution
of oxalic acid saturated in the cold, solution of borax, solution
of alum at 10 per cent., and solution of ammonium molybdate at
33¹/₃ per cent. ought not to extract any coloring matter at a
boiling heat. The borax extract, if subsequently treated with
hydrochloric acid, should not turn red, nor become blue on the
further addition of ferric chloride. Solutions of stannous chloride
and ferric chloride with the aid of heat ought entirely to destroy
the blue coloring matter. Glacial acetic acid on repeated boiling
should entirely dissolve the coloring matter. If the acetic
extracts are mixed with two volumes of ether and water is added, so
as to separate out the ether, the water should appear as a slightly
blue solution, the main bulk of the indigo remaining in suspension
at the surface of contact of the ethereal and watery stratum. This
acid watery stratum should be colorless, and should not assume any
color if a little strong hydrochloric acid is allowed to fall into
it through the ether. No sulphureted hydrogen should be evolved on
boiling the yarn or cloth in strong hydrochloric acid. On prolonged
boiling, supersaturation with strong potassa in excess, heating and
adding a few drops of chloroform, no isonitrile should be
formed.—W. Lenz.

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