Scientific American Supplement, No. 561, October 2, 1886
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Title: Scientific American Supplement, No. 561, October 2, 1886
Author: Various
Release date: July 27, 2005 [eBook #16360]
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Language: English
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*** START OF THE PROJECT GUTENBERG EBOOK SCIENTIFIC AMERICAN SUPPLEMENT, NO. 561, OCTOBER 2, 1886 ***
Produced by Juliet Sutherland, Jeannie Howse, Victoria
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[Illustration]
SCIENTIFIC AMERICAN SUPPLEMENT NO. 561
NEW YORK, OCTOBER 2, 1886
Scientific American Supplement. Vol. XXII., No. 561.
Scientific American established 1845
Scientific American Supplement, $5 a year.
Scientific American and Supplement, $7 a year.
* * * * *
TABLE OF CONTENTS.
I. BOTANY.--A Century Plant in Bloom.--Interesting account of
the recent blossoming of an _Agave Americana_ at
Auburn, N.Y. 8965
Alpine Flowers in the Pyrenees.--1 illustration. 8965
II. CHEMISTRY.--Probable Isolation of Fluorine.--Decomposition
of hydrofluoric acid by an electric current.--By M.H.
MOISSAN.--Production of a new body, possibly fluorine, or
perfluoride of hydrogen. 8963
The Determination of Nitric Acid by the Absorption of Nitric
Oxide in a Standard Solution of Permanganate of Potash.--
By H.N. MORSE and A.F. LINN. Full description of a new and
important volumetric determination.--1 illustration. 8964
Water of Crystallization.--By W.W.J. NICOL, M.A., D.Sc.--
Discussion of the state of water of crystallization in a
salt in solution. 8964
III. ENGINEERING.--Combustion, Fire Boxes, and Steam Boilers--By
JOHN A. COLEMAN.--Address before the June Convention of
the Master Mechanics' Association. 8953
Compound Hydraulic Presses.--Different forms of presses
designed for pressing bales for shipment.--Very fully
illustrated by 8 figures. 8951
Examination Papers in General Construction.--Eighty-six
questions in engineering propounded by the civil service
examiners of New York city. 8956
IV. MEDICINE AND PHYSIOLOGY.--A New Apparatus for the Study of
Cardiac Drugs.--By WILLIAM GILMAN THOMPSON, M.D.--Ingenious
application of instantaneous photography to the study
of heart movements.--Apparatus and views produced.--3
illustrations. 8966
Creosote a Specific for Erysipelas,--A new cure for this
complaint. 8966
V. METALLURGY.--Primitive Iron Manufacture.--Iron furnace
and blowing apparatus in use in Bengal.--2 illustrations. 8962
VI. MINING ENGINEERING.--The Catastrophe at Chancelade.--
Application of photography to investigating mine disasters.
--4 illustrations. 8962
VII. MISCELLANEOUS.--Celebration of the 500th Anniversary of the
University of Heidelberg. August, 1886. 8957
Useful Bags and How to Make Them.--Interesting paper on the
trunk makers' art.--4 illustrations. 8960
VIII. NAVAL ENGINEERING.--Atlantic Steamers.--By W. JOHN.--
Exhaustive comparison of representative Atlantic liners
and war ships.--3 illustrations. 8954
Jet Propellers.--Hydraulic propulsion of vessels.--
Mathematical examination of this subject. 8951
IX. ORDNANCE.--The New Army Gun.--Description of the 8-inch
steel gun as manufactured at the West Point, N.Y.,
Foundry.--1 illustration. 8952
X. PHYSICS.--A New Thermo Regulator.--1 illustration. 8959
Cohesion and Cohesion Figures.--By WILLIAM ACKROYD,
F.I.C.--Laws of vortex rings examined, and relation of
solubility to cohesion. 8963
Pipette for taking the Density of Liquids.--Apparatus and
calculations for use.--1 illustration. 8959
XI. TECHNOLOGY.--Impurities in Photographic Chemicals, and
Tests for Same.--Table referred to in a paper read before
the Birmingham Photographic Society by G.M. Jones, M.P.S. 8957
Molasses, how made.--Work on Plantations Graphically
Described.* 8961
Optical errors and human mistakes.--By ERNST GUNDLACH.--On
the examination of optical glasses.--A paper read before
the Buffalo meeting of the A.A.A.S. 8963
Soap.--By HENRY LEFFMANN, Ph.D. 8962
Somzee's New Gas Burners.--Interesting description of
regenerative burners.--9 figures. 8958
The Clamond Gas Burner.--Of value as a supplement to the
above named article, describing an incandescent burner.
--1 illustration. 8959
Wood Oil.--A new industry worked on the large scale in
Sweden. 8962
* Transcriber's Note: "Work on Plantations..." was
originally part of TOC entry "Optical Errors..."
* * * * *
COMPOUND HYDRAULIC PRESSES.
In a hydraulic packing press, the work done by the ram during one
stroke may be roughly divided into two periods, in the first of which
the resistance, although gradually increasing, may be called light,
while in the second the resistance is heavy. The former of these two
periods embraces the greater part of the stroke, and it is only a
small proportion at the end which requires the exercise of the full
power of the press to bring the material to the determined degree of
consolidation. Consequently, if a hydraulic press is to be worked so
as to waste no time, it requires to be provided with means by which
its table may be made to rise rapidly during the portion of the stroke
when the resistance is small, and afterward more slowly when the
entire power of the pumps is being expended upon the final squeeze.
Many methods of obtaining this end have been devised, and are in
common use both here and abroad. It is, however, more particularly in
the packing of raw material that such appliances are useful, since the
goods pressed into bales in this country are not usually of a very
yielding nature, and consequently do not require a long stroke to
bring them to a high state of compression. In India and Egypt, from
whence cotton is sent in bales, presses must have a long stroke; and
unless they can be worked rapidly, a very considerable amount of plant
is required to get through a moderate quantity of work. To meet the
necessities of these countries, Mr. Watson has devised several forms
of press in which not only is the table made to rise rapidly through
the greater part of its stroke, but the rams are kept almost
constantly in motion, so that the time occupied in filling the box
with raw cotton and in placing the ties round the bales is not lost.
[Illustration: COMPOUND HYDRAULIC PRESS. FIGS. 1 and 2.]
We illustrate four forms of Mr. Watson's presses, Fig. 1 being an
earlier construction, which, although very rapid at the date at which
it was brought out, has been far surpassed in celerity by the
arrangements shown in Figs. 3 to 8. It was introduced in 1873, and
forty-three presses according to this design were sent to India by the
makers, Messrs. Fawcett, Preston & Co., of Phoenix Foundry,
Liverpool, between that year and 1880. Four presses of this kind are
worked by one engine, having a cylinder 20 in. by 3 ft. stroke, and
driving eighteen to twenty pumps of varying diameter and short stroke.
The press has two long-stroke rams, LL, of small diameter, to compress
the loose material, and two short-stroke rams, FF, of large diameter,
to give the final squeeze. These two pairs of rams act alternately,
the one pair being idle while the other is in operation. The lashing
of the bale takes place while the larger rams are in action, the bale
being supported on the grid, B, which is pushed under it through
grooves formed in the press-head, S (Fig. 1). When the grid is in
place the press-head can be lowered, and the box be filled, while the
bale is receiving its final squeeze from the inverted rams above.
In Figs. 1 and 2 the press is shown in the position it would occupy if
the bale, M, were just completed and ready to be pushed out, and the
box, N, were full of material. The filling doors, CC, are shown turned
back level with the floor, the main doors, AA, are open, as are also
the end doors, KK, to admit the men to fasten up the bale. If water be
admitted to the subsidiary cylinder, H, the head, G, and two rams, FF,
will be raised, and then the bale, M, can be thrown out finished. All
the doors are now closed and water admitted to the rams, LL. These
immediately rise, pushing the contents of the box, N, before them, and
compressing them until the table, S, reaches the level of the grid, B.
At this moment the tappet rod, D, shuts off the water, and withdraws
the bolt of the doors, AA, which fly open. The grid, B (Fig. 2), is
then run through the grooves in the press-head, S, and the rams, LL,
are allowed to descend ready for a baling cloth to be inserted through
the doors, EE, and for the box, N, to be refilled. At the same time
the head, G, comes down on to the bale and compresses it still
further, while the men are at work lashing it. When the material is in
hanks, like jute, the rams, LL, are lowered slowly, while a man
standing inside the box, at about the level of the floor, packs the
material neatly on the table.
These presses can be worked with great rapidity, the average output
during a day varying from 21 to 28 bales an hour. The consumption of
coal per bale is 9 lb. of Bengal coal, in value about ¾d. The density
of the cotton bales produced is about 45 lb. per cubic foot, 400 lb.
measuring a little under 9 cubic feet for shipment. In the case of
jute or jute roots, the same weight occupies 10 cubic feet on an
average. But rapid as this press is in action, the necessities of
recent business in India have called for still more expeditious
working, and to meet this demand Mr. Watson produced his compound
press, in which the economy of time is carried to its utmost
development. By the addition of a second pair of long-stroke rams the
output of the press has been trebled, being raised to 80 bales per
hour. To effect this, there is one pair of powerful rams, as in the
press just described, but two pairs of the long-stroke rams. Further,
each pair of the small-diameter rams is fitted with two boxes, one of
which is always being filled while the other is being pressed. The
rams in rising compress the material into a small cell or box,
situated above the box in which raw cotton is thrown. On the top of
the ram head there is a loose lashing plate, which, at the finish of
the action of the rams, is locked in the cell by bolts actuated by a
suitable locking gear. While in this cell the bale has the lashing
ropes put round it, and then it is placed under the large rams for the
final squeeze, during which the ties or ropes are permanently secured.
Thus neither of the small presses has even to wait while its box is
being filled, or while the previously pressed bale is being lashed.
Even in the large press, when the ties are finally fastened, the time
occupied does not exceed three-quarters of a minute, and is often much
less.
[Illustration: COMPOUND HYDRAULIC PRESS. FIGS. 3 and 4.]
This press is shown in Figs. 3 and 4. The small rams are arranged at
either side of the large ones, which, in this case, are not inverted.
To each of the smaller presses there is a pair of boxes mounted on a
vertical column, around which they can revolve to bring either box
over the rain head. When the left hand rams rise, the material is
delivered into the cell, D, which previously has had its doors (Fig.
4) closed. To permit of the cell, D, being moved out of the way, it is
mounted so that it can revolve on one of the columns of the main
press, first into the position shown at B (Fig. 4), and afterward to C
(Fig. 3). While at D, the bale in the cell (called from its
construction a revolver) is partly lashed, the ties or ropes being put
into position. It is then rotated until it comes over the large rams,
where the bale is still more compressed and secured.
It must be admitted that this press provides for the greatest possible
economy of time, and for the largest output, for the capital employed,
which can be attained. The rams and the men are constantly in action,
and not a single moment is lost. For filling each box 78 seconds are
allowed, and there is ample time for the preliminary lashing.
[Illustration: COMPOUND HYDRAULIC PRESS. FIGS. 5 and 6.]
Figs. 5 and 6 show a modification of this press, designed to turn out
sixty bales per hour. It has only one set of long-stroke rams, with
three revolvers. The bale receives its preliminary lashing while in
the position, B (Fig. 6). Fifty-three seconds are available for
filling the box, and the same time for the preliminary lashing. It is
found, however, that three-quarters of a minute is sufficient for the
complete hooping of a bale.
[Illustration: COMPOUND HYDRAULIC PRESS. FIGS. 7 and 8.]
Figs. 7 and 8 show a similar press intended for jute pressing. This
has only one box, which is fixed, as the material has to be packed in
an orderly manner. Its speed is sixty bales an hour.--_Engineering._
* * * * *
JET PROPELLERS.--HYDRAULIC PROPULSION OF VESSELS.
Certain mechanical devices appear to exercise a remarkable influence
on some minds, and engineers are blamed for not adopting them, in no
very measured terms in some cases. It is not in any way necessary that
these devices should have been invented by the men who advocate their
adoption, in order to secure that advocacy. The intrinsic attractions
of the scheme suffice to evoke eulogy; and engineers sometimes find it
very difficult to make those who believe in such devices understand
that there are valid reasons standing in the way of their adoption.
One such device is hydraulic propulsion. A correspondent in a recent
impression suggested its immediate and extended use in yachts at all
events, and we willingly published his letter, because the system does
no doubt lend itself very freely to adoption for a particular class of
yachts, namely, those provided with auxiliary power only. But because
this is the case it must not be assumed that the jet propeller is
better than screw or paddle-wheel propulsion; and it is just as well,
before, correspondence extends further, that we should explain why and
in what way it is not satisfactory. The arguments to be urged in favor
of hydraulic propulsion are many and cogent; but it will not fail to
strike our readers, we think, that all these arguments refer, not to
the efficiency of the system, but to its convenience. A ship with a
hydraulic propeller can sail without let or hindrance; a powerful pump
is provided, which will deal with an enormous leak, and so on. If all
the good things which hydraulic propulsion promises could be had
combined with a fair efficiency, then the days of the screw propeller
and the paddle wheel would be numbered; but the efficiency of the
hydraulic propeller is very low, and we hope to make the reason why it
is low intelligible to readers who are ignorant of mathematics. Those
who are not ignorant of them will find no difficulty in applying them
to what we have to say, and arriving at similar conclusions in a
different way.
Professor Greenhill has advanced in our pages a new theory of the
screw propeller. As the series of papers in which he puts forward his
theory is not complete, we shall not in any way criticise it; but we
must point out that the view he takes is not that taken by other
writers and reasoners on the subject, and in any case it will not
apply to hydraulic propulsion. For these reasons we shall adhere in
what we are about to advance to the propositions laid down by
Professor Rankine, as the exponent of the hitherto received theory of
the whole subject. When a screw or paddle wheel is put in motion, a
body of water is driven astern and the ship is driven ahead. Water,
from its excessive mobility, is incapable of giving any resistance to
the screw or paddle save that due to its inertia. If, for example, we
conceive of the existence of a sea without any inertia, then we can
readily understand that the water composing such a sea would offer no
resistance to being pushed astern by paddle or screw. When a gun is
fired, the weapon moves in one direction--this is called its
recoil--while the shot moves in another direction. The same
principal--_pace_ Professor Greenhill--operates to cause the movement
of a ship. The water is driven in one direction, the ship in another.
Now, Professor Rankine has laid down the proposition that, other
things being equal, that propeller must be most efficient which sends
the largest quantity of water astern at the slowest speed. This is a
very important proposition, and it should be fully grasped and
understood in all its bearings. The reason why of it is very simple.
Returning for a moment to our gun, we see that a certain amount of
work is done on it in causing it to recoil; but the whole of the work
done by the powder is, other things being equal, a constant quantity.
The sum of the work done on the shot and on the gun in causing their
motions is equal to the energy expended by the powder, consequently
the more work we do on the gun, the less is available for the shot. It
can be shown that, if the gun weighed no more than the shot, when the
charge was ignited the gun and the shot would proceed in opposite
directions at similar velocities--very much less than that which the
shot would have had had the gun been held fast, and very much greater
than the gun would have had if its weight were, as is usually the
case, much in excess of that of the shot. In like manner, part of the
work of a steam engine is done in driving the ship ahead, and part in
pushing the water astern. An increase in the weight of water is
equivalent to an augmentation in the weight of our gun and its
carriage--of all that, in short, takes part in the recoil.
But, it will be urged, it is just the same thing to drive a large body
of water astern at a slow speed as a small body at a high speed. This
is the favorite fallacy of the advocates of hydraulic propulsion. The
turbine or centrifugal pump put into the ship drives astern through
the nozzles at each side a comparatively small body of water at a very
high velocity. In some early experiments we believe that a velocity of
88 ft. per second, or 60 miles an hour, was maintained. A screw
propeller operating with an enormously larger blade area than any pump
can have, drives astern at very slow speed a vast weight of water at
every revolution; therefore, unless it can be shown that the result is
the same whether we use high speed and small quantities or low speed
and large quantities, the case of the hydraulic propeller is hopeless.
But this cannot be done. It is a fact, on the contrary, that the work
wasted on the water increases in a very rapid ratio with its speed.
The work stored up in the moving water is expressed in foot pounds by
the formula
W v² / 2g
where W stands for the weight of the water, and v for its velocity.
But the work stored in the water must have been derived from the
engine; consequently the waste of engine power augments, not in the
ratio of the speed of the water, but in the ratio of the square of its
speed. Thus if a screw sends 100 tons of water astern at a speed of 10
ft. per second per second, the work wasted will be 156 foot tons per
second in round numbers. If a hydraulic propeller sent 10 tons astern
at 100 ft. per second per second, the work done on it would be 1,562
foot tons per second, or ten times as much. But the reaction effort,
or thrust on the ship, would be the same in both cases. The waste of
energy would, under such circumstances, be ten times as great with the
hydraulic propeller as with the screw. In other words, the slip would
be magnified in that proportion. Of course, it will be understood that
we are not taking into account resistances, and defects proper to the
screw, from which hydraulic propulsion is free, nor are we considering
certain drawbacks to the efficiency of the hydraulic propeller, from
which the screw is exempt; all that we are dealing with is the waste
of power in the shape of work done in moving water astern which we do
not want to move, but cannot help moving. If our readers have followed
us so far, they will now understand the bearing of Rankine's
proposition, that that propeller is best which moves the greatest
quantity of water astern at the slowest speed. The weight of water
moved is one factor of the thrust, and consequently the greater that
weight, other things being equal, the greater the propelling force
brought to bear on the ship.
It may be urged, and with propriety, that the results obtained in
practice with the jet propeller are more favorable than our reasoning
would indicate as possible; but it will be seen that we have taken no
notice of conditions which seriously affect the performance of a
screw. There is no doubt that it puts water in motion not astern. It
twists it up in a rope, so to speak. Its skin frictional resistance is
very great. In a word, in comparing the hydraulic system with the
normal system, we are comparing two very imperfect things together;
but the fact remains, and applies up to a certain point, that the
hydraulic propeller must be very inefficient, because it, of all
propellers, drives the smallest quantity of water astern at the
highest velocity.
There is, moreover, another and a very serious defect in the hydraulic
propeller as usually made, which is that every ton of water passed
through it has the velocity of the ship herself suddenly imparted to
it. That is to say, the ship has to drag water with her. To illustrate
our meaning, let us suppose that a canal boat passes below a stage or
platform a mile long, on which are arranged a series of sacks of corn.
Let it further be supposed that as the canal boat passes along the
platform, at a speed of say five miles an hour, one sack shall be
dropped into the boat and another dropped overboard continuously. It
is evident that each sack, while it remains in the boat, will have a
speed the same as that of the boat, though it had none before. Work
consequently is done on each sack, in overcoming its inertia by
imparting a velocity of five miles an hour to it, and all this work
must be done by the horse towing on the bank. In like manner the
hydraulic propeller boat is continually taking in tons of water,
imparting her own velocity to them, and then throwing them overboard.
The loss of efficiency from this source may become enormous. So great,
indeed, is the resistance due to this cause that it precludes the
notion of anything like high speeds being attained. We do not mean to
assert that a moderate degree of efficiency may not be got from
hydraulic propulsion, but it can only be had by making the quantity of
water sent astern as great as possible and its velocity as small as
possible. That is to say, very large nozzles must be employed. Again,
provision will have to be made for sending the water through the
propeller in such a way that it shall have as little as possible of
the motion of the ship imparted to it. But as soon as we begin to
reduce these principles to practice, it will be seen that we get
something very like a paddle wheel hung in the middle of the boat and
working through an aperture in her hull, or else a screw propeller put
into a tube traversing her from stem to stern.
We may sum up by saying that the hydraulic propeller is less efficient
than the screw, because it does more work on the water and less on the
boat; and that the boat in turn does more work on the water than does
one propelled by a screw, because she has to take in thousands of tons
per hour and impart to them a velocity equal to her own. Part of this
work is got back again in a way sufficiently obvious, but not all. If
it were all wasted, the efficiency of the hydraulic propeller would be
so low that nothing would be heard about it, and we certainly should
not have written this article.--_The Engineer._
* * * * *
THE NEW ARMY GUN.
The cut we give is from a photograph taken shortly after the recent
firings. The carriage upon which it is mounted is the one designed by
the Department and manufactured by the West Point Foundry, about six
months since. It was designed as a proof carriage for this gun and
also for the 10 inch steel gun in course of construction. It is
adapted to the larger gun by introducing two steel bushing rings
fitted into the cheeks of carriage to secure the trunnion of the gun.
The gun represented is an 8 inch, all steel, breech-loading rifle,
manufactured by the West Point Foundry, upon designs from the Army
Ordnance Bureau. The tube and jacket were obtained from Whitworth, and
the hoops and the breech mechanism forgings from the Midvale Steel
Company. The total weight of the gun is 13 tons; total length,
including breech mechanism, 271 inches; length of bore in front of gas
check, 30 calibers; powder space in chamber, 3,109 cubic inches;
charge, 100 pounds. The tube extends back to breech recess from
muzzle, in one solid piece. The breech block is carried in the jacket,
the thread cut in the rear portion of the jacket. The jacket extends
forward and is shrunk over the tube about 87½ inches. The re-enforce
is strengthened by two rows of steel hoops; the trunnion hoops form
one of the outer layers. In front of the jacket a single row of hoops
is shrunk on the tube and extends toward the muzzle, leaving 91 inches
of the muzzle end of the tube unhooped. The second row of hoops is
shrunk on forward of the trunnion hoops for a length of 38 inches to
strengthen the gun, and the hoop portion forms three conical frustums.
The elastic resistance of the gun to tangential rupture over the
powder chamber is computed by Claverino and kindred formulas to be
54,000 lb. per square inch.
[Illustration: THE ARMY 8 INCH STEEL GUN WITH CARRIAGE.]
The breech mechanism is modeled after the De Bange system. The block
has three smooth and three threaded sectors, and is locked in place by
one-sixth of a turn of a block, and secured by the eccentric end of a
heavy lever, which revolves into a cut made in the rear breech of the
gun. The gas check consists of a pad made of two steel plates or cups,
between which is a pad of asbestos and mutton suet formed under heavy
pressure. The rifling consists of narrow grooves and bands, 45 of
each. The depth of the groove is six one-hundredths of an inch.
Although the gun is designed for a charge of 100 pounds, it is
believed that it can be increased to 105 pounds without giving
dangerous pressure, and the intention is to increase the charge to
that amount when the new powder is received from Du Pont.
The following is a very full synopsis of the official report of the
preliminary firings--13 rounds--with this gun:
The first seven rounds were fired with German cocoa powder, which was
received from Watervliet Arsenal. There were two kinds of cartridges,
one kind weighing 85 pounds, and having 30 grains in each layer, the
other weighing 100 lb., and having 27 grains in each layer. In two of
the first seven rounds the weight of the charge was 65 pounds, the
projectiles weighing 182 and 286 pounds; in the next two rounds
charges of 85 pounds were fired, the projectiles, as before, weighing
182 and 286 pounds, while in the last three of the rounds fired with
cocoa powder the charge was 100 lb., while the weight of the
projectile was 182, 235, and 286 pounds. At the seventh round was
fired the normal charge, 100 lb. of powder and a projectile weighing
286 pounds, for which the gun was designed. The mean pressure for this
round, determined by two crusher gauges, was 32,800 pounds, and the
velocity at 150 feet was 1,787 feet.
Two kinds of Du Pont's brown prismatic powder, marked P.A. and P.I.,
were then fired. With the normal charge of P.A. powder (round 12 of
the record), the mean pressure was 35,450 pounds, the velocity at 150
feet was 1,812 feet. For P.I. powder (round 13 of the record), the
pressure was 26,925 pounds, the velocity was 1,702 feet, and a
considerable amount of unconsumed powder was ejected, showing that the
P.I. powder is not a suitable one for this piece. The highest pressure
indicated with the normal charge of P.A. powder was 36,200 pounds,
exceeding by 1,200 pounds the provisional limit of pressure.
At the fifth round the breech block opened with some difficulty, and
an examination showed that the resistance resulted from the diametral
enlargement of the rear plate. Directions have been given to correct
this defect. The star gauge records show that no material change took
place in the diameter of the chamber or the bore. From 30 inches to 54
inches (measured from base of the breech), there was a diminution in
diameter of from 0.001 in. to 0.002 in.; in rear of 30 inches there
was no change. No enlargement in the shot chamber exceeded 0.001 in.
From the bottom of the bore (the beginning of the rifling) to the
muzzle the average enlargements were as follows: in. to 6 in., 0.005
in.; 7 in. to 14 in., 0.003 in.; 15 in. to 29 in., 0.002 in.; 30 in.
to muzzle, 0.002 to 0.001 in.
After the third round the joint between the D. and D. rings opened
slightly on the top, and measured after the 13th round showed that the
opening was about 0.004 in. wide. It cannot at present be stated
whether or not this opening increased during firing, but the defect
has been noted and will be carefully observed. Enough cocoa powder
remains to allow a comparison to be made with such brown prismatic
powder as may be adopted finally. No firing has been done as yet to
test the best position for the bands, but it will take place as soon
as enough of some standard powder is obtained to fire ten consecutive
rounds.--_Army and Navy Journal._
* * * * *
COMBUSTION, FIRE-BOXES, AND STEAM BOILERS.[1]
[Footnote 1: Address before the June Convention of the Master
Mechanics' Association.]
By JOHN A. COLEMAN.
Mr. Chairman and gentlemen: I was rash enough some time ago to promise
to prepare a paper for this occasion, the fulfillment of which prior
engagements have absolutely prevented.
I would greatly prefer to be let off altogether, but I do not like to
break down when expected to do anything; and if you have the patience
to listen for a few minutes to the reflections of an "outsider," I
will endeavor to put what I have to say in as concise form as I can,
in such manner as will do no harm, even if it does no good.
For many years I was connected with steam engineering. I was once with
the Corliss Steam Engine Company, and afterward was the agent of Mr.
Joseph Harrison, of Russian fame, for the introduction of his safety
boilers.
That brought me into contact with the heavy manufacturers throughout
the Eastern States, and during that long experience I was particularly
impressed with a peculiarity common to the mill owners, which, I
believe it may be said with truth, is equally common to those
interested in locomotive engineering, namely, how much we overlook
common, every-day facts. For instance, we burn coal; that is, we think
we do, and boilers are put into mills and upon railroads, and we
suppose we are burning coal under them, when in reality we are only
partially doing so. We think that because coal is consumed it
necessarily is burned, but such is frequently very far from the fact.
I wish upon the present occasion to make merely a sort of general
statement of what I conceive to be combustion, and what I conceive to
be a boiler, and then to try to make a useful application of these
ideas to the locomotive.
Treating first the subject of combustion, let us take the top of the
grate-bars as our starting point. When we shovel coal upon the grate
bars and ignite it, what happens first? We separate the two
constituents of coal, the carbon from the hydrogen. We make a gas
works. Carbon by itself will burn no more than a stone; neither will
hydrogen. It requires a given number of equivalents of oxygen to mix
with so many equivalents of carbon, and a given number of equivalents
of oxygen to mix with so many of hydrogen to form that union which is
necessary to produce heat. This requires time, space, and air, and one
thing more, viz., heat.
I presume that most of you have read Charles Williams' treatise upon
"Combustion," which was published many years ago, and which until
recently was often quoted as an absolute authority upon the art of
burning fuel under boilers. Mr. Williams in his treatise accurately
describes the chemistry of combustion, but he has misled the world for
fifty years by an error in reasoning and the failure to discuss a
certain mechanical fact connected with the combination of gases in the
process of combustion. He said: "What is the use of heating the air
put into a furnace? If you take a cubic foot of air, it contains just
so many atoms of oxygen, neither more nor less. If the air be heated,
you cause it to assume double its volume, but you have not added a
single atom of oxygen, and you will require twice the space for its
passage between the grate bars, and twice the space in the furnace,
which is a nuisance; but if the air could be frozen, it would be
condensed, and more atoms of oxygen could be crowded into the cubic
foot, and the fire would receive a corresponding advantage." Mr.
Williams proceeded upon this theory, and died without solving the
perplexing mystery of as frequent failure as success which attended
his experiments with steamship boilers. The only successes which he
obtained were misleading, because they were made with boilers so badly
proportioned for their work that almost any change would produce
benefit.
Successful combustion requires something more than the necessary
chemical elements of carbon, hydrogen, and oxygen, for it requires
something to cook the elements, so to speak, and that is heat, and for
this reason: When the coal is volatilized in the furnace, what would
be a cubic foot of gas, if cold, is itself heated and its volume
increased to double its normal proportion. It is thin and attenuated.
The cold air which is introduced to the furnace is denser than the
gas. With dampers wide open in the chimney, and the gases and air
passing into the flues with a velocity of 40 feet per second, they
strike the colder surface of the tubes, and are cooled below the point
of combustion before they have had time to become assimilated; and
although an opponent in a debate upon steam boiler tests once stated
that his thermometer in the chimney showed only 250 degrees, and
indicated that all the value that was practical had been obtained from
the coal, I took the liberty to maintain that a chemist might have
analyzed the gases and shown there were dollars in them; and that if
the thermometer had been removed from the chimney and placed in the
pile of coal outside the boiler, it would have gone still lower; but
it would not have proved the value to have been extracted from the
coal, for it was not the complete test to apply.
The condition of things in the furnace may be illustrated thus: If we
should mingle a quart of molasses and a gallon of water, it would
require considerable manipulation and some time to cause them to
unite. Why? Because one element is so much denser than the other; but
if we should mix a quart of the gallon of water with the quart of
molasses, and render their densities somewhere near the density of the
remaining water, and then pour the masses together, there would be a
more speedy commingling of the two. And so with the furnace. I have
always maintained that every furnace should be lined with fire-brick,
in order that it shall be so intensely hot when the air enters that
the air shall instantly be heated to the same degree of tenuity as the
hot gases themselves, and the two will then unite like a flash--and
that is heat. And here is the solution of the Wye Williams mystery of
failure when cold air was introduced upon the top of a fire to aid
combustion. The proof of the necessity for heat to aid the chemical
assimilation of the volatilized coal elements is seen in starting a
fire in a common stove. At first there is only a blue flame, in which
the hand may be held; but wait until the lining becomes white hot, and
then throw on a little coal, and you will find a totally different
result. It is also seen in the Siemens gas furnace, with which you are
doubtless familiar. There is the introduction of gas with its
necessary complement of air. Until the furnace and retorts become
heated, the air and gas flutter through only partially united, and do
little good; but as soon as the retorts and furnace become thoroughly
hot, the same gas and air will melt a fire-brick.
These are common phenomena, which are familiar, but apt to be
unnoticed; but they logically point to the truth that no furnaces
should present a cooling medium in contact with fuel which is
undergoing this process of digestion, so to speak. It will be very
evident, I think, from these facts that water-legs in direct contact
with a fire are a mistake. They tend to check a fire as far as their
influence extends, as a thin sheet of ice upon the stomach after
dinner would check digestion, and for the same reason, namely, the
abstraction of heat from a chemical process. If fire-brick could be
laid around a locomotive furnace, and the grate, of course, kept of
the same area as before, it is my belief that a very important
advantage would be at once apparent. An old-fashioned cast iron heater
always produced a treacherous fire. It would grow dead around the
outside next to the cold iron; but put a fire-clay lining into it, and
it was as good as any other stove.
If I have now made clear what I mean by making heat, we will next
consider the steam boiler. What is a steam boiler? It is a thing to
absorb heat. The bottom line of this science is the bottom of a pot
over a fire, which is the best boiler surface in the world; there is
water upon one side of a piece of iron and heat against the other. One
square foot of the iron will transmit through it a given number of
units of heat into the water at a given temperature in a given time;
two square feet twice as many, and three, three times as many, and so
on. Put a cover upon the pot, and seal it tight, leave an orifice for
the steam, and that is a steam boiler with all its mysteries.
The old-fashioned, plain cylinder boiler is a plain cylindrical pot
over the fire. If enough plain cylinder boilers presenting the
requisite number of square feet of absorbing surface are put into a
cotton mill, experience has shown that they will make a yard of cotton
cloth about as cheaply as tubular boilers. If this is so, why do not
all put them in? Because it is the crudest and most expensive form of
boiler when its enormous area of ground, brickwork, and its fittings
are considered. Not all have the money or the room for them. To
produce space, the area is drawn in sidewise and lengthwise, but we
must have the necessary amount of square feet of absorbing surface,
consequently the boiler is doubled up, so to speak, and we have a
"flue boiler." We draw in sidewise and lengthwise once more and double
up the surface again, and that is a "tubular boiler." That includes
all the "mystery" on that subject.
Now, we find among the mills, just as I imagine we should upon the
railroads, that the almost universal tendency is to put in too small
boilers and furnaces. To skimp at boilers is to spend at the coal
yard. Small boilers mean heavy and over-deep fires, and rapid
destruction of apparatus. In sugar houses you will see this frequently
illustrated, and will find 16 inch fires upon their grates.
We have found that, as we could persuade mill owners to put in more
boilers and extend their furnaces, so that coal could be burned
moderately and time for combustion afforded, we often saved as high as
1,000 tons in a yearly consumption of 4,000.
Now, when the ordinary locomotive sends particles of coal into the
cars in which I am riding, I do not think it would be unfair criticism
to say that the process of combustion was not properly carried out.
When we see dense volumes of gas emitted from the stack, it is evident
that a portion of the hard dollars which were paid for the coal are
being uselessly thrown into the air; and it will be well to remember
that only a little of the unburnt gas is visible to the eye.
One point I wish to make is this: We find, as I have said, that as we
spread out with boilers and furnaces in the mills, so that we can take
matters deliberately, we save money.
Now, coming again to locomotives. I think, if we examine the subject
carefully, the fact will strike us a little curiously. The first
locomotive built in Philadelphia weighed about 14 tons. Judging from
the cut I have seen, I should think her furnace might have been 30
inches square. We have gone from that little 14 ton engine to machines
of 50 and 60 tons--perhaps more. The engines have been increased over
four times, but I will ask you if the furnace areas have been
increased (applause) in proportion? Some of the furnaces of the
engines are six feet by three, but that is an increase of less than 3
to 1 of furnace, as against 4 to 1 of weight of engine.
When my attention was first called to this matter, I had supposed, as
most people do who are outside of the railway profession, that there
was something subtile and mysterious about railway engineering that
none but those brought up to the business could understand. Possibly
it is so, and I am merely making suggestions for what they are worth,
but I think the position I have taken in this matter was established
by some experiments of three weeks' duration, which I conducted
between Milan and Como, in Italy, for the Italian government, in
pulling freight trains up grades of 100 feet to the mile. The
experiments were made with an engine built by the Reading Railroad.
We competed with English, French, Belgian, and Austrian engines. These
machines required the best of fuel to perform the mountain service,
and could use coal dust only when it was pressed into brick. We used
in the Reading Railroad machine different fuels upon different days,
making the road trip of 120 miles each day with one kind of fuel. We
used coal dust scraped up in the yards, also the best Cardiff coal,
anthracite, and five kinds of Italian lignite, the best of which
possesses about half the combustible value of coal.
The results in drawing heavy freight trains were equally good with
each fuel, the engine having at all times an abundance of steam on
heavy grades, no smoke nor cinders, and no collection of cinders in
the forward part of the engine.
The fireman arranged his fires at a station, and did little or nothing
except to smoke his pipe and enjoy the scenery until he reached the
next station. An incident occurred to prove that we were not playing
with the machine. They told me one morning that we should be given a
load of 25 per cent less than the maximum load of an engine of her
class (30 tons). We started up the 100 foot grade, and found we could
barely crawl, and our engineer got furious over it. He thought they
were repeating a trick already attempted by screwing down a brake in
ascending a grade. We detected it, however, and found a pair of wheels
nearly red hot. Upon this occasion we found nothing amiss, except full
cars where they had reported only a light load. We pulled to the top
of the hill, the steam blowing off furiously all the time.
This was a new experience to the Italians, and might surprise some
Americans. When we arrived at the station, the inspector-general and
his corps of engineers were evidently amazed, and it was evident we
had captured them. He said to me, "I can congratulate you, signor, on
possession of a superb machine."
Afterward one of the engineers said to me: "Do not let it be known
that I told you what you have hauled or I shall lose my place, but you
have drawn 50 per cent more than the maximum load of one of our 40 ton
engines." I said: "You attempted to 'stall' us, and when you try it
again, be fair enough to give me a flat of pig iron, and as you pack
cars on one end I will pack pig iron upon the engine until she will
stick to the track, but rest assured that you will not be able to get
that steam down." The experience with that engine proves conclusively
to my mind that the general principles of steam making are the same
for both stationary and locomotive practice. The grand secret of the
success of that Wootten engine was the enormous area of the grate
surface, being, if I remember correctly, 7 by 9 feet, permitting thin
fires to be carried and complete combustion to be obtained before the
gases reached the boiler tubes. An enormous crown sheet was presented,
and that is where the bulk of the work of any boiler is done.
Thin fires accomplish this. As already stated, a given amount of coal
generates a given amount of gas, and this gas requires a given amount
of air or oxygen. This air must be supplied through the grate bars and
then pass through the interstices of the mass of heated coal. It
requires about 10 cubic feet of air to consume one cubic foot of gas.
In stationary boilers we find that if we use "pea" and "dust" coal, an
extremely thin layer must be used, or the 10 feet of air per foot of
gas cannot pass through it; if "chestnut" coal be used, the thickness
may be increased somewhat; "stove size" allows a thickness of six
inches, and "lump" much thicker, if any wise man could be found who
would use that coarse, uneconomical size. Of course, I am speaking of
anthracite coal. Opinions differ about "soft coal," but the same
general principle applies as regards an unobstructed passage of air
through the hot bed of coal.
Now, it will be agreed that the locomotive of the future must be
improved to keep up with the times. Fierce competition requires
increased efficiency and reduced expenses. I am told by you railroad
gentlemen that the freight business of the country doubles every ten
years. Trains follow close upon each other. What are you going to do?
Are you to double, treble, or quadruple your tracks?
It seems to me much remains yet to be done with the locomotive. We
must burn a great deal less coal for the steam we make, and after we
have made steam we must use that steam up more thoroughly. In the
short cylinder required by locomotive service, the steam, entering at
the initial pressure pushes the piston to the opposite end, and it
then rushes out of the exhaust strong enough to drive another piston.
Of every four dollars' worth of coal consumed, at least two dollars
worth is absolutely thrown away. Or, of every ten thousand dollars
spent for fuel, five thousand dollars are absolutely wasted. How can
we save this? It would seem obvious that if steam rushes from the
exhaust of an engine strong enough to drive another engine, the common
sense of the thing would be to put another engine alongside and let
the steam drive it, and we should get just so much more out of our
four dollars' worth of coal. It seems evident that we must follow the
lead of the steamship men, and compound the locomotive engine, as
they have done with the marine engine.
Next we must attack the extravagant furnace, and increase its area and
reduce the depth of the bed of coal. The difficulty of making this
change seemed to me to be removed, on examining an engine on the
Providence & Bristol Railroad, the other day. The machine was made at
the Mason Works, of Taunton. It was an engine and tender combined, the
truck being at the rear end of the tender, and the driver placed well
in advance of the fire-box, so that the maximum weight of both engine
and tender rested upon the drivers. In thus removing the drivers from
the proximity of the fire-box, abundant facility is afforded for
widening the fire-box, so as to obtain a grate area as large as that
of the Wootten engine or of a stationary boiler. It seems to me the
increase of grate area can be obtained only by widening; for a length
of more than six or seven feet is very hard upon the fireman. You
certainly cannot get more power by deepening present fire-boxes,
except by an enormously increased waste of fuel, which all will
concede is already sufficiently extravagant.
In arriving at the conclusion of these hasty and I fear somewhat
incoherent remarks, I would say that the object aimed at for the
improvement of the locomotive would be reached, first, by making steam
economically, by employing such increased grate area as will permit
running thin fires and moderate or comparatively slow draught; and,
secondly, in economically using the steam which has been economically
made by compounding the engine.
I have given you merely the views of an "outsider," who has had a
somewhat extensive experience in stationary engineering, and who has
observed locomotive practice in many parts of the world. These views
are offered for what they are worth, as suggestions for future thought
in designing engines, and as a sort of refresher upon rudimentary
points which long familiarity with every-day phenomena causes us at
times to overlook. I trust that your deliberations may aid in the
speedy reduction of the expenses of transporting freight and
passengers, for the benefit of the railroad companies and, in their
turn, the advantage of the people at large.
* * * * *
ATLANTIC STEAMERS.[1]
[Footnote 1: A paper recently read before the Institution of Naval
Architects.]
By W. JOHN.
[Illustration: Fig. 1--CITY OF ROME.]
The author said that he hoped to bring before the meeting impartially
certain facts which might be of interest, and which, when recorded in
the pages of the "Transactions," might be found of some use as data
for future reference. In dealing with passenger steamers, he would do
so principally from a shipbuilder's point of view; but the moment he
commenced to think over Atlantic passenger ships as a shipbuilder, he
was met by the question whether the present tendency toward divorcing
the passenger and cargo trade from each other is likely to continue or
not. If the answer is yes, then it seems to become an important
question, for the present at least, how to build, on moderately small
dimensions, the fastest, safest, and most economical passenger
steamer, using all the most modern improvements to make her commodious
and luxurious, and an easy sea boat into the bargain. If cargo is
still to be carried in the passenger ships of the future, a moderate
speed only will be aimed at in the immediate future, and every effort
will be devoted to economy of fuel, comfort, and safety, with a fair
carrying capacity. This latter policy is one which may possibly
prevail at least for a time, as it has powerful supporters in
Liverpool; but he could not help thinking that very high
speeds--higher than we have yet attained--must eventually gain the
day. He also thought that they were on the eve of important movements,
which will indicate what the next step in the passenger trade is to
be; for it must be remembered, among other things, that none of our
present English transatlantic liners, even the latest, have yet been
fitted with the latest modern improvements for economy of fuel or
quick combustion, such as triple expansion engines or forced draught.
They must, therefore, be at some disadvantage, other things being
equal, compared with the ships of the future possessing them. The
Great Eastern steaming up Milford Haven about twenty-five years ago
between two lines of the channel fleet of old--two and three decked
wooden line-of-battle ships--the whole fleet saluting with yards
manned, was a sight to be remembered. More than this, that ship, with
all her mournful career, has been a useful lesson and a useful warning
to all naval architects who seriously study their profession--a lesson
of what can be done in the safe construction of huge floating
structures, and a warning that the highest flights of constructive
genius may prove abortive if not strictly subordinated to the
practical conditions and commercial requirements of the times. The
Sirius and Great Western crossed the Atlantic in 1838, and in 1840 the
first ship of the since celebrated Cunard Company made her first
voyage. This was the Britannia, which, with her sister ships, the
Arcadia, Caledonia, and Columbia, kept up the mail service regularly
at a speed of about 8½ knots an hour. The Britannia was 207 ft. in
length between perpendiculars, and 34 ft. 4 in. extreme breadth, 22
ft. 6 in. depth of hold, 423 horse power--nominal--and 1,153 tons
burden, built of wood, and propelled by paddles. In 1860 the Collins
Line started in opposition to the Cunard, and, after a series of
disasters, collapsed in 1858. This was three years after the Persia,
the first Cunarder built of iron, had been completed. In 1850, also,
the Inman Line was started with the City of Glasgow, of 1,600 tons
builders' measurement, and 350 horse power. She was built of iron, and
was the first screw steamer sent across the Atlantic from Liverpool
with passengers, and was the pioneer of the great emigrant trade which
Mr. Inman, above all others, did so much to develop and make cheap and
comfortable for the emigrants themselves, as well as profitable to his
company. That the builders of the celebrated old Great Britain, in
1843, and Mr. Inman, in 1850, should have pronounced so decisively in
favor of the screw propeller in preference to the paddle for ocean
steaming is a proof of their true practical judgment, which time and
practical experience have made abundantly clear. While the Cunard
Company went on developing its fleet from the early wood paddle
steamer Britannia of 1,130 tons in 1840 to the iron paddle steamers
Persia, etc., in 1858, the iron screw steamer China of 1862, to the
still more important screw steamers Bothnia and Scythia, vessels of
4,335 tons, in 1874, the Inman and other lines were as rapidly
developing in speed and size, if not in numbers. The year 1874 is
memorable, for it saw the White Star steamers Britannic and Germanic
put into the water, as well as the Inman steamer City of Berlin and
the two before mentioned Cunard steamers, Bothnia and Scythia. By the
addition of these two ships to their fleet the White Star Line,
although started only in 1870, reached a front rank position in the
New York passenger trade. The author gave in separate tables the logs
of several of these ships, some from published documents and some
kindly furnished by the owners. The Great Western had crossed the
Atlantic from Bristol to New York in 15 days as early as 1838. The
first Cunard steamer, the Britannic, was about the same speed, from 8¼
to 8½ knots an hour. The average duration of the Cunard voyages in the
year 1856 was 12.67 days from Liverpool to New York, and 11.03 days
from New York to Liverpool. The Bothnia, in 1874, reduced the passage
to about nine days. The White Star Britannic, in 1876, averaged 7 days
18 hours 26 minutes outward from Queenstown to New York, and 9 days 6
hours 44 minutes homeward, and has averaged for the last ten years 8
days 9 hours 36 minutes outward, and 8 days 1 hour 48 minutes
homeward. The City of Berlin, of the Inman Line, also built in 1874, 8
days 10 hours 56 minutes, and homeward 8 days 2 hours 37 minutes; and
for the nine years from 1875 to 1883 inclusive, averaged outward 8
days 19 hours 56 seconds, and inward 8 days 8 hours 34 seconds; or,
putting it into rounder figures, the Britannic had reduced the average
passage between the two points to 8¼ days, and the City of Berlin to
8½ days. From the year 1874 on to 1879 no further advance was made in
Atlantic steaming, but in that year the Arizona was added to the Guion
Line, and it soon became evident that another important stride had
been made in the Atlantic passenger trade, which would lead to most
important results. The results, as we all know, have been sufficiently
startling. The Guion Line, which had started in 1866 with the
Manhattan, had now the fastest passenger ship on the Atlantic. In
spite of burning some fifty per cent. more coal than the Britannic,
the ship was an obvious commercial success. The spirited policy which
brought her into existence was appreciated by the public, and the
other lines had to move forward. Then followed a period of rivalry,
the Cunard Company building the Gallia and Servia, the Inman Company
the City of Rome, and the Guion Line the Alaska, all of which were
completed in 1881, and afterward the Oregon for the Guion
Line--1883--the Aurania the same year for the Cunard Company, and,
later still, the America for the National Line, and the Umbria and
Etruria for the Cunard Company in 1885.
[Illustration:
_Frames from outer edge of Tank to Upper Deck, 7 × 3½ × 8/16 for 250
ft. Amidships, for 60 ft. before and abaft these Points 6½ × 3½ × 6/16
at end of Vessel 5 × 3½ × 7/16, all spaced 24 in. apart and all
carried to Upper Deck, double from Bilge to Bilge in way of
Engines.--Frames in Tank on Lattice and Solid Floors, 5 × 3½ × 8/16,
Intermediate Frames, 8 × 4 × 9/16--Rev: Frames, 4½ × 3½ × 8/16,
carried to Upper and Main Deck alternately double, 4½ × 4½ × 8/16 from
Bilge to Bilge in E and B space._
Fig. 2--SERVIA.]
Since the completion of the Etruria, for various reasons there has
been a pause in the tremendous strides made since 1879, and we may
briefly review the results. Taking the Britannic as a standard with
her ten years' average of 8¼ days across, and her quickest passage of
7 days 10 hours 53 seconds, we have now the following steamers of
higher speeds. Taking them in the order of their absolutely fastest
passage out or home, they stand thus:
TABLE I.
---+-------------------------+------+-------+------
| | Days.| Hours.| Mins.
| +------+-------+------
1 | Etruria. | 6 | 5 | 31
2 | Umbria (sister ship). | slightly longer.
3 | Oregon. | 6 | 10 | 35
4 | America. | 6 | 13 | 44
5 | City of Rome. | 6 | 18 | 0
6 | Alaska. | 6 | 18 | 37
7 | Servia. | 6 | 23 | 55
8 | Aurania. | 7 | 1 | 1
---+-------------------------+------+-------+------
It will thus be seen that from the 15 days' passage or thereabout, of
the earliest Atlantic steamers, we had got down in the days of the
Scotia to about 9 days; in the Britannic to 8¼ days, and, at the
present time, we have got to 6¼ days, with seven ships afloat that
have done the passage under seven days, and capable of making their
average passages range between 6½ and 7¼ days.
Ranged in order of gross tonnage, these eight vessels stand as
follows:
TABLE II.
1. City of Rome. 8,144
2. Oregon. 7,375
3. Aurania. 7,269
4. Servia. 7,212
5. Umbria. 7,129
6. Etruria. 7,100
7. Alaska. 6,586
8. America. 5,528
Here the America shows to advantage, for while being eighth in size
she is fourth in point of speed, and from what the author can learn,
although he had no authenticated details on the subject, he believed
she is economical in coal consumption. He might perhaps be permitted
to say that one of the most difficult subjects in connection with the
propulsion of ships on which to get absolutely accurate data is that
of coal consumption. The records of six to eight hours' trials for the
purpose of ascertaining the coal consumption are absolutely worthless,
as all shipbuilders and engineers know, and so far as English ships
are concerned they are never attempted. Foreign owners frequently
stipulate for such trials in their contracts with English
shipbuilders, and get wonderfully economical results on paper, but the
fact that the trials only extend over a few hours renders them
valueless, however carefully the coal may be weighed during that
period. An authentic record of the absolute quantity of coal consumed,
say by each of the eight fastest Atlantic liners, together with their
average indicated horse power on the voyage, for a series of voyages,
would be extremely valuable.
He gave, in Table III., the consumption per indicated horse power per
hour for a number of ships. This table affords valuable data, for it
gives, in addition to the dimensions, the moulded draught of water,
the midship area, the displacement, the indicated horse power, the
speed on trial, the coefficients for the lines both from the block or
parallelopipedon, and also from the midship section prism, together
with the length and angle of entrance obtained by Kirk's rule, the
Admiralty displacement coefficient, together with the coal consumption
per day and per indicated horse power per hour.
[Illustration: Fig. 3--OREGON.]
This table, as will be seen, contains some of the most important of
the Atlantic liners, and also a number of other typical ships, which
will add a variety to its interest and a value to it. The coefficient,
which is contained in the thirteenth column of the table, viz.:
Dis 2/3 × speed³
-------------------------
I.H.P. × sqrt(entrance.)
---------------
10
generally comes out for ships of similar type more nearly a constant
in the true sense of the word than the corresponding Admiralty
constant. As an example, we have the curves of resistance and horse
power for the City of Rome and the Normandie, a large vessel of 6,000
tons, which the Barrow Company built for the Compagnie Generale
Transatlantique, in which the coefficient of fineness and the form of
the lines pretty closely resemble each other below water; and if we
take from the curves the corresponding speeds and horse powers, and
work out the constants by the two systems, we have at 14 knots the
Admiralty constant for the City of Rome 322.2, and for the Normandie
304.8; and taking for a modified form of constant, the City of Rome
gives 253.7 and the Normandie 251.9, which, as will be seen, are much
closer together. Similarly, at 15 knots the Admiralty constant for the
City of Rome is 310, and for the Normandie 295.2, while a modified
constant comes out for the former at 245, and for the latter 244,
again agreeing almost identically. The same at 16 knots, for the City
of Rome the Admiralty constant comes out 297.6, and for the Normandie
282.8, while a modified constant comes out for the two ships 234.4 and
233.7 respectively, again showing marked agreement. It may be
mentioned that in these two ships the engines are of a similar type,
being three-crank tandem engines, and the propellers have in both
pitch and surface practically the same proportions to the power and
speed. The value of these modified constants will probably be found to
increase as the speeds increase up to the limit and beyond that point
at which wave resistance becomes an important factor.
TABLE III
----------------+--------+---------+---------+-------+-------------+
Name. |Length. | Breadth.| Moulded |Midship|Displacement.|
| | | draught.| area. | |
| | | | | |
| | | | | |
| | | | | |
----------------+--------+---------+---------+-------+-------------+
|ft. in. | ft. in. | ft. in. | | |
| | | | | |
City of Rome | 542 6 | 52 0 | 21 5½ | 1031 | 11,230 |
| | | | | |
| | | | | |
Normandie | 459 4 | 49 11 | 19 9¾ | 892 | 7,975 |
| | | | | |
Furnessia | 445 0 | 44 6 | 22 2½ | 893 | 8,578 |
| | | | | |
| | | | | |
Arizona | 450 0 | 45 1½ | 18 9 | 758 | 6,415 |
| | | | | |
| | | | | |
Orient | 445 0 | 46 0 | 21 4½ | 904 | 7,770 |
| | | | | |
| | | | | |
Stirling Castle | 420 0 | 50 0 | 22 3 | 990 | 7,600 |
| | | | | |
| | | | | |
Elbe | 420 0 | 44 9 | 20 0 | 807 | 6,350 |
| | | | | |
Pembroke Castle | 400 0 | 42 0 | 17 0 | 648 | 5,130 |
| | | | | |
Umbria and | | | | | |
Etruria | 500 0 | 57 0 | 22 6 | 1090 | 9,860 |
| | | | | |
| | | | | |
Aurania | 470 0 | 57 0 | 20 0 | 1020 | 8,800 |
| | | | | |
| | | | | |
America | 441 8 | 51 3 | ----- | --- | 6,500 |
| | | | | |
| | | | | |
Oregon | 501 0 | 54 2 | 23 8 | 1150 | 11,000 |
| | | | | |
| | | | | |
Servia | 515 0 | 52 0 | 23 3½ | 1046 | 10,960 |
| | | | | |
Scotia, P.S. | 369 0 | 47 6 | 19 9 | 867 | 6,000 |
| | | | | |
| | | | | |
Alaska | 500 0 | 50 0 | 21 0 | 949 | 9,210 |
| | | | | |
| | | | | |
Aller | 438 0 | 48 0 | 21 0 | 907 | 7,447 |
| | | | | |
| | | | | |
| | | | | |
Ems | 430 0 | 46 10 | 20 7½ | 877 | 7,030 |
----------------+--------+---------+---------+-------+-------------+
----------------+----------+---------+-----------+-----------+-----------+
Name |Indicated | Speed. | Block | Midship | Prismatic |
| H.P. | |coefficient| section | midship |
| | | |coefficient| section |
| | | | |coefficient|
| | | | | |
| | | | | |
----------------+----------+---------+-----------+-----------+-----------+
| | | | | |
| | | | | |
| | | | | |
City of Rome | 11,890 | 18.235 | .649 | .925 | .702 |
| | | | | |
| | | | | |
Normandie | 6,959 | 16.66 | .614 | .901 | .681 |
| | | | | |
Furnessia | 4,045 | ¹14 | .682 | .903 | .755 |
| | | | | |
| | | | | |
Arizona | 6,300 | 17 | .589 | .895 | .658 |
| | | | | |
| | | | | |
Orient | 5,433 | 15.538 | .621 | .919 | .676 |
| | | | | |
| | | | | |
Stirling Castle | 8,396 | 18.4 | .569 | .889 | .639 |
| | | | | |
| | | | | |
Elbe | 5,665 | 16.571 | .591 | .901 | .655 |
| | | | | |
Pembroke Castle | 2,435.8 | 13.25 | .623 | .623 | .692 |
| | | | | |
Umbria and | | | | | |
Etruria | 14,321 | 20.18 | .538 | .896 | .637 |
| | | | | |
| | | | | |
Aurania | 8,500 | ¹17.5 | .575 | .942 | .632 |
| | | | | |
| | | | | |
America | ----- | ¹17.8 | ---- | ---- | ---- |
| | | | | |
| | | | | |
Oregon | 13,300 | 18.3 | .599 | .849 | .67 |
| | | | | |
| | | | | |
Servia | 10,300 | ¹16.9 | .610 | .862 | .71 |
| | | | | |
Scotia, P.S. | 4,632 | ¹14.31 | .605 | .92 | .65 |
| | | | | |
| | | | | |
Alaska | ----- | ---- | .614 | .904 | .679 |
| | | | | |
| | | | | |
Aller | 7,974 | 17.9 | .590 | .899 | .656 |
| | | | | |
| | | | | |
| | | | | |
Ems | 7,251 | 17.55 | .593 | .907 | .652 |
----------------+----------+---------+-----------+-----------+-----------+
----------------+------------+-----------------+-----------------+
Name. | D 2/3 × S³ | D 2/3 × S³ | Kirk's system. |
| ---------- | --------------- | |
| I.H.P. | _____ +---------+-------+
| |I.H.P. × \/ent. |Length of|Angle. |
| | ------- |entrance.| |
| | 10 | | |
----------------+------------+-----------------+---------+-------+
| | | | |
| | | | |
City of Rome | 255 | 201.3 | 161.27 | 8° 29'|
| | | | |
| | | | |
Normandie | 265 | 219.5 | 146.41 | 8° 44'|
| | | | |
Furnessia | 284 | 273 | 108.7 |10° 28'|
| | | | |
| | | | |
Arizona | 269.2 | 217 | 153.79 | 7° 30'|
| | | | |
| | | | |
Orient | 270.8 | 225 | 144.17 | 8° 21'|
| | | | |
| | | | |
Stirling Castle | 286.8 | 233.7 | 151.3 | 8° 22'|
| | | | |
| | | | |
Elbe | 275.5 | 229 | 144.6 | 7° 56'|
| | | | |
Pembroke Castle | 284 | 258 | 122.9 | 8° 49'|
| | | | |
Umbria and | | | | |
Etruria | 260 | 191.8 | 184 | 6° 52'|
| | | | |
| | | | |
Aurania | 266 | 204.6 | 170 | 8° 38'|
| | | | |
| | | | |
America | --- | --- | --- | ----- |
| | | | |
| | | | |
Oregon | 227.9 | 190 | 164.3 | 9° 39'|
| | | | |
| | | | |
Servia | 231 | 192 | 145.3 |10° 42'|
| | | | |
Scotia, P.S. | 208.9 | 186 | 126.8 |13° 21'|
| | | | |
| | | | |
Alaska | --- | --- | 160.23 | 8° 2'|
| | | | |
| | | | |
Aller | 277 | 225 | 150.6 | 8° 10'|
| | | | |
| | | | |
| | | | |
Ems | 273 | 223 | 149.4 | 8° 40'|
----------------+------------+-----------------+---------+-------+
----------------+------------+--------------------+----------------+--------+
Name. | Coal | Cylinders | Boilers | Working|
|consumption | | |Pressure|
|-----+------+-------------+------+--------+-------+ |
| Per | Per | Diameter |Stroke|Heating | Bar | |
| day |I.H.P.| | |surface |surface| |
| | | | | | | |
----------------+-----+------+-------------+------+--------+-------+--------+
| | | Ins. | Ins. | | | lbs. |
| | |/3 @ 46 \| | | | |
City of Rome | 185 | 2.2 |\3 @ 86 /| 72 | 29,286 | 1398 | 90 |
| | | | | | | |
| | |/3 @ 35-7/16\| | | | |
Normandie | 148 | 2 |\3 @ 74-7/8 /| 67 | 21,404 | 756 | 85.2 |
| | | | | | | |
Furnessia | 97 | 2.2 | 49-100 | 66 | 10,396 | 440 | 90 |
| | | | | | | |
| | |/1 @ 62 \| | | | |
Arizona | --- | --- |\2 @ 90 /| 66 | ---- | ---- | 90 |
| | | | | | | |
| | |/1 @ 60 \| | | | |
Orient | --- | --- |\2 @ 85 /| 60 | ---- | ---- | 75 |
| | | | | | | |
| | |/1 @ 62 \| | | | |
Stirling Castle | --- | --- |\2 @ 90 /| 66 | 21,161 | 787 | 100 |
| | | | | | | |
| | |/1 @ 60 \| | | | |
Elbe | --- | --- |\2 @ 85 /| 60 | ---- | ---- | --- |
| | | | | | | |
Pembroke Castle | 44 | 1.7 | 43 and 86 | 57 | 7,896 | 288 | 99 |
| | | | | | | |
Umbria and | | |/1 @ 71 \| | | | |
Etruria | 315 | 2.1 |\2 @ 105 /| 72 | 38,817 | 1606 | 110 |
| | | | | | | |
| | |/1 @ 68 \| | | | |
Aurania | 215 | 2.2 |\2 @ 91 /| 72 | 23,284 | 1001 | --- |
| | | | | | | |
| | |/1 @ 63 \| | | | |
America | 185 | --- |\2 @ 91 /| 66 | ---- | 882 | --- |
| | | | | | | |
| | |/1 @ 70 \| | | | |
Oregon | 310 | 2.2 |\2 @ 104 /| 72 | 38,047 | 1428 | 110 |
| | | | | | | |
| | |/1 @ 72 \| | | | |
Servia | 205 | 2 |\2 @ 100 /| 78 | 27,483 | 1014 | --- |
| | | | | | | |
Scotia, P.S. | 168 | 3.4 | | -- | ---- | ---- | --- |
| | | | | | | |
| | |/1 @ 68 \| | | | |
Alaska | --- | --- |\2 @ 100 /| 72 | ---- | ---- | 100 |
| | | | | | | |
| | |/1 @ 44 \| | | | |
Aller | --- | --- ||1 @ 70 || 72 | 22,630 | 799 | 150 |
| | |\1 @ 100 /| | | | |
| | | | | | | |
| | |/1 @ 62 \| | | | |
Ems | --- | --- |\2 @ 86 /| 60 | 19,700 | 780 | 100 |
----------------+-----+------+-------------+------+--------+-------+--------+
¹Mean speed of a voyage across the Atlantic Ocean.
The author next considered the strains to which a ship is exposed, and
stated that he had before him the calculations for three of the
largest vessels, two of them of iron and the other of steel; and he
found, in the case of the iron, the maximum tension on the gunwale
during the greatest hogging strains likely to be endured at sea would
not exceed about six tons per square inch, while in the case of the
steel ship it is only about 6½ tons. These strains are well within the
limits of safety, and a comparison of the scantlings of these with the
others justifies the assertion as to their general safety from a
structural point of view. The sections of these three ships are shown
in Figs. 1, 2, and 3, with their principal scantlings. It will be seen
from these sections that the three ships differ materially in their
mode of construction. In the case of Fig. 1, which represents the City
of Rome, the largest of the three, it will be seen that the main
framing of the vessel is entirely transverse, with very heavy keelsons
in the bottom, and large partial bulkheads or web frames, and the
outside plating arranged on what is termed the edge to edge principle,
with a great portion of it double. In the next section, Fig. 2, the
Servia, which is built of steel, on the other hand, the bottom is
built on the longitudinal cellular system, the first application, he
believed, of this system to an Atlantic liner. The plating of the
Servia is of the usual alternate outer and inner strake system, partly
double; while the third section, the Oregon, approaches more nearly to
the ordinary system of framing and plating usually adopted, but it
will be seen that she was well tied in the bottom by very heavy
intercostal and plate keelsons, as well as in the top by heavy
stringers and sheer strakes, with much of her plating doubled, and
heavy web frames inside. The author next considered the question of
stability, and went on to deal with the subject of twin screws, and
stated that the Barrow Shipbuilding Company has done more in the way
of planning and designing for the adoption of twin screws lately than
for any other mode of propulsion, and this chiefly for passenger
steamers. He did not attach much importance to the particular form of
the blade either in single or twin screws, as he believed so long as
the disk area, the surface, and pitch were properly adjusted to the
speed of the vessel, and to enable the engines to use, at the maximum
speed, just the full quantity of steam that the boilers can make, we
have got pretty nearly as far as we can get. To fix these dimensions
of the propeller accurately at the present time, and without further
knowledge of the action of the screw on the water, was, he thought,
impossible. All the rules and formulæ are empirical. The best one he
knew is given in Table IV., due to Mr. Thom, the head of the Barrow
Company's engineering drawing office, and at present acting manager,
who has used it for some years in practice. These formulæ are based
upon the assumption that the area of propeller disk should be
proportional to the indicated horse power, divided by the cube of the
speed, and the same with the projected area of the propeller and also
the surface.
TABLE IV.
_Particulars of Propellers and Constants._
------------------------------+-------+---------+----------+--------------
| Length| | Proj. | Feet per
Ship. | of | Disk | surf. | minute.
| ship. |constant.| constant.|Speed of tips.
------------------------------+-------+---------+----------+--------------
City of Rome. | 542 | 220 | 69 | 4,715
Normandie | 459 | 250 | 66 | 4,099
Furnessia | 445 | 223 | 69 | 3,654
Eden | 300 | 211 | 64 | 3,080
Yorouba | 270 | 213 | 63 | 3,202
Taygete | 260 | 238 | 56 | 3,166
Kow-shing | 250 | 171 | 69 | 3,369
S.Y. Monarch | 152 | 221 | 65 | 4,040
S.Y. Aries | 138 | 179 | 56 | 2,986
Twin screw Fenella | 200 | 244 | 64 | 2,890
Twin screw H.M.S. Fearless[2] | 220 | 277 | 67 | 5,022
Twin screw H.M.S. Iris | --- | 454[6]| 135[6] | ---
Twin screw H.M.S. Iris [3] | 300 | 412 | 221 | ---
Twin screw H.M.S. Iris [4] | 300 | 346 | 99 | 4,961
Twin screw H.M.S. Iris [5] | 300 | 439 | 82 | 5,309
------------------------------+-------+---------+----------+-------------
[Footnote 2: Estimated with a speed of 17.5 knots and 3,370
I.H.P.]
[Footnote 3: With the first propeller at the estimated speed of
17.5 knots and 7,000 I.H.P.]
[Footnote 4: With four bladed modified Griffith's on actual
trial.]
[Footnote 5: With two bladed modified Griffith's on actual trial.]
[Footnote 6: Constants obtained from first propeller calculated
from a speed of 18.5 knots and 7,500 I.H.P.
Area of propeller disk × speed of ship in knots.³
Disk constant = --------------------------------------------------
I.H.P.
Projected Projected area of propeller × speed of ships in knots.³
area = ------------------------------------------------------
of constants I.H.P.
Expanded area constants may be obtained and used in the same way.]
The discussion which followed was opened by Mr. Holt. He said that if
they were to have greater speed on the Atlantic, there was one point
which was not alluded to in the paper, and that was the total
abolition of cargo on board the great passenger steamers. If vessels
were built solely for passenger traffic, they would be able to insure
greater speed by reason of the greater slightness in build and the
additional space at the command of the designer. The existing Atlantic
express steamer was far too heavy, and might, if cargo was dispensed
with, be made with finer lines and more yacht-like. He looked on the
proposition to fit such vessels with longitudinal bulkheads with great
fear. If a collision took place--such, for example, as that which sunk
the Oregon--water would get access to one side only of the ship, and
it was not at all improbable that if a sea was on, she would turn
right over. At all events, very serious risk would be involved.
Mr. W.H. White, Chief Constructor to the Admiralty, said the question
of twin screw propulsion was one of special interest to himself, and
had been so for many years. In 1878 he dealt with it as fully as he
then could on the basis of the Admiralty data, and he then ventured to
say everything in favor of twin screws that Mr. John had said in his
paper. If greater power than that now used in such a ship as the
Etruria, for example, were demanded, two screws must be used. Good as
are the results obtained with the Etruria, it was by no means certain
that still better might not be had. If she had been fitted with two
screws instead of one, very great advantage would be gained by the
greater submergence of the twin screws, as thus racing would be almost
wholly prevented.
Mr. Calvert urged that more attention should be devoted to studying
the relative values of different portions of the propeller.
The sitting was then suspended. In the afternoon, as we have already
stated, the members visited the steamship Germanic on the invitation
of Messrs. Ismay, Imrie & Co., subsequently proceeding to Messrs. Cope
Brothers' tobacco works, and thence to the exhibition, where the
dinner of the Institution took place in the evening.
On Friday morning no paper was read; some official business was
transacted, and this being done, the discussion on Mr. John's paper
was resumed.
Mr. Biles remarked that there were many advantages in the use of twin
screws which had not been sufficiently taken into account. When a ship
with twin screws was being handled in dock there was greater
maneuvering power, and therefore less liability for the ship to come
in contact with the walls, although, if she did so, there would be
greater probability of damage to the propellers. He thought means
could be easily devised of protecting the screws when the ship was in
dock. Another of the incidental advantages connected with twin screws
was that smaller engines and smaller propellers were required, and
therefore they might run them at a higher speed. They would also get
lighter machinery with twin screws, and there would be less liability
to have bad castings and forgings in the smaller engines, and of
course the cost would be less.
With respect to the question of the middle line bulkheads, he could
not quite agree with Mr. John as to the great advantages of them in a
big passenger steamer. He thought there would be greater difficulty in
managing a ship so built if she was in danger of sinking. Increased
subdivision in a longitudinal direction was a very desirable thing,
and almost necessary for a condition of immunity from sinking. In
future Atlantic steamers longitudinal bulkheads should be placed not
in the middle line, but nearer the sides of the ships, and they should
recognize the fact that they had engines and boilers in different
compartments, and make arrangements whereby the ship would still
float, although the doors in these compartments were kept open. The
proper way to arrive at that was to have a ship with great beam, and
to have two longitudinal bulkheads at considerable distances from the
sides of the ship, subdivided as completely as possible, both under
and above water, so that, even supposing they got water into the space
between one bulkhead and the side of the ship, they would have
sufficient buoyancy in the other parts of the ship to keep her afloat.
Broad ships must necessarily mean deep ships, in order to have comfort
at sea. They were limited in length, and first came the question how
many passengers they wanted to carry. The experience of a ship like
the America--which was only 400 ft. in length--showed it was not
necessary to go to great length to have great speed. A ship of 400 ft.
to 430 ft. in length, 65 ft. of beam, and with a depth of 45 ft.,
would be a ship of proper dimensions for the Atlantic trade, and he
believed it quite possible to build a vessel of special construction
of about 7,000 tons gross register which should steam with less
consumption of coal than the Umbria and Etruria at a rate of 22 knots,
crossing the Atlantic from Liverpool to New York in six days. He
thought that was likely to be the vessel of the future, and that it
would be quite as commercially successful as the Umbria or Etruria.
Mr. J. Campbell remarked that at present the great American liners had
only the ordinary compound engines, and he thought that, instead of
converting them to triple expansion, they should take a step further
at once, and adopt quadruple expansion engines. This class of engines
was being very successfully built in various parts of the country. He
should recommend the adoption of a three-crank six-cylinder engine.
Mr. Hamilton did not think it had been demonstrated that greater
efficiency had been got out of twin screws than out of single screws;
but there was no doubt they would tend to additional safety.
Mr. Martell said that when they had got satisfactory data, twin screws
would be adopted for ships requiring great speed; but they had not got
that data at present.
Admiral Sir John Hay, referring to twin screws as applying to
sea-going steamers which might be employed for imperial defense, said
it was quite certain that the defense of their extended commerce
would always require to be assisted by ships such as the Oregon and
other magnificent vessels which had been used for that purpose on a
recent occasion. He believed that for war purposes the twin screw was
recognized by all naval men as having very many advantages. If that
were so, it was quite evident that it would be a great advantage,
under such conditions as occurred at the loss of the Oregon, if the
compartments could be made completely water-tight; and the twin screw,
with the separation of the ship longitudinally, gave them the very
greatest possible protection. They could not trust to bulkheads that
were only closed occasionally by doors. What was required for war
purposes was the entire and complete isolation of different parts of
the ship, having always practically closed communications between
them.
Mr. John then replied on the general discussion. He was pleased to
find that they had faith in the future of the twin screw and of
subdivision. The public had a right to demand greater safety than they
at present had on the Atlantic, or could have with a single screw.
* * * * *
EXAMINATION QUESTIONS IN GENERAL CONSTRUCTION.
The following is a copy of the last examination paper given to
candidates who are desirous of employment in the constructive
departments of the municipality of New York:
N.B.--In case candidate does not remember formula or method of solving
any problem submitted to him, let him name any work upon the subject
where such formula or method may be found.
1. What is civil engineering?
2. Have you ever pursued a course of study in any educational
institution, or with any civil engineer, which would fit you for the
position of assistant engineer? If so, state when and with whom; state
also, in detail, what experience you have had.
3. Have you ever had responsible charge of any public work? If so,
state particulars.
4. Solve the following according to the algebraic signs:
--------------------------------------
/ (6-2/7 - 4-3/9) × 8-7/16
/ ------------------------ × 67873.367, and show your work.
\/ 4-4/12
5. The population of a certain town in 1880 was 7,095; it having
increased 25 per cent. in ten years, what was it in 1870? Show your
work.
6. How many feet, board measure, in the flooring of a room 20 feet by
30 feet and 2½ inches thick?
7. Find value of x and y in the following equations:
2 x + 3 y = 33
4 x - y = 17.
8. Find value of x in equation x² - x - 40 = 170.
9. Find value of x in equation
--------
a / a² - x² x
- + / ------- = -
b \/ x² b
10. Explain the meaning of the expression a½ × b¾.
11. What is a logarithm?
12. What is the base of the common system?
13. In making what calculations are logarithms useful?
14. How do you find the logarithm of a number in a table of
logarithms?
15. What are similar triangles?
16. How are similar triangles proportioned to each other?
17. The sides of a polygon being prolonged, what is the sum of all the
exterior angles equal to?
18. How do you pass the circumference of a circle through three given
points not in the same straight line?
19. How do you describe a square in a circle?
[Illustration]
20. In the triangle, b being a right angle, what proportion does d b
bear to a d and d c?
21. How do you inscribe a regular hexagon in a circle?
22. What proportion do circumference and areas of circles bear to
their radii?
23. How do you find the area of a regular polygon?
24. Of an irregular polygon?
25. Of a circle?
26. How do you find the solid contents of a cylinder?
27. Of a wedge?
28. Of a pyramid?
29. Find the contents of the wedge, base 20 feet by 30 feet, height 10
feet, edge 15 feet.
30. State the prismoidal formula; would you use it in calculating
earthwork?
31. Is a simple question in calculating areas.--Ed. _Eng. News_.
32. How many and what parts of a plane triangle must be given to find
the rest?
33. Define the terms sine, co-sine, tangent, and co-tangent.
34. What are natural sines, co-sines, etc.?
35. What is a table of logarithmic sines, co-sines, etc.?
30. Two sides and two angles of a plane triangle being given, how do
you find the other parts?
37. When two sides of a plane triangle and their included angles are
given, how do you find the other parts?
38. In the right-angled triangle, A B H express algebraically the
value of the sine, co-sine, tangent, and co-tangent of angle A in
terms of a, b, and h, they being the altitude, base, and hypothenuse
of the triangle.
39. What is the law of gravitation?
40. Do you understand that there is any difference in the meaning of
the terms gravitation and gravity?
41. What is the law of falling bodies?
42. Express algebraically this law, taking v = velocity of falling
body; g = acceleration of gravity; and h = height.
43. What is the center of gravity of a body?
44. How is it found?
45. Where is the center of gravity of a homogeneous body whose sides
are all rectangles?
46. What is the specific gravity of a body?
47. What is the standard for solids and liquids?
48. What for gases?
49. What laws govern the pressure of liquids at rest?
50. How do you find the number of gallons of water to the cubic foot?
51. What is the weight of a gallon of water?
52. What is the pressure per square inch on the side of a vessel at
the depth of 10 feet below the surface of the water?
53. What will be the theoretical volume of discharge per second from a
reservoir through a pipe 1 foot in diameter, discharging at a depth of
100 feet below the surface of the water?
54. How many gallons of water will be discharged through a pipe 1 foot
in diameter, 328 feet long, head 13½ feet, coefficient of flow =
0.007?
55. State how many men are needed to make up a full party for a survey
of a preliminary line or location of a public work, such as a railroad
or aqueduct.
56. State also their several duties.
57. For what purpose is the magnetic needle used in surveying land?
58. What is a traverse table and for what used?
59. How do you set out a circular curved line upon the ground?
60. If an obstacle occurs to alignment, state how you would overcome
it upon straight lines, also upon curves.
61. The radius of a curve being given, and angle of intersection of
the two tangents, how do you find the length of the tangent from their
intersection to the beginning of the curve?
62. Describe an engineer's transit, and name its adjustments.
63. Describe a Y level, and name its adjustments.
64. How many kinds of leveling rods do you know of?
65. State how they are graduated, and how they can be read to the
1/1000 of a foot.
66. Show a form of field-book for transit notes used when "running"
curves, and place thereon notes of a 5 deg. curve for 1,000, with two
intermediate "set-ups."
67. Show a form of level-book, and place therein sufficient figures to
show your method.
68. What are cross-sections?
69. How do you set slope stakes for excavation and embankment?
70. What is a grade line?
71. What proportion of the breaking weight of a beam would you
consider a safe load?
72. With the load uniformly distributed, what fractional part of the
whole weight may be considered, in all calculations, as being carried
at the center?
73. Suppose a beam supported at both ends, and take w = weight, l =
length of beam, b = breadth, d = depth, s = breaking weight. Express
algebraically the value of s in terms of the other quantities.
74. Sectional area being 36 square inches, which would be the stronger
section, 6 by 6 or 4 by 9?
75. Make a design for a pair of rafters, connected by a tie-beam, for
a roof 30 feet span, showing the dimensions of the several parts and
the manner of connecting them. State in detail your method of
obtaining the several dimensions.
76. How do you apply the principle of the parallelogram of forces in
determining the strain on the various members of a structure?
Illustrate graphically.
77. What should be the thickness at the top and base of a retaining
wall 15 feet high, built to retain ordinary earth? Show your method of
obtaining the required dimensions, also a sketch of the wall, showing
how it should be founded.
78. A reservoir is to be built, depth of water 10 feet. If the walls
are built of masonry, find the thickness of the same, and state how
they should be built. Show your work.
79. What is an arch, of how many forms, and of what may it be
constructed?
80. Can you state how you would find the thickness of an arch of
stone, span and rise being given?
81. Define the intrados and extrados of an arch.
82. Where should the line of resistance to pressure be found in an
arch in order to retain its stability?
83. Can you find the thickness of the abutments, the rise and span of
the arch being given?
84. In a semicircular arch, where is the horizontal thrust greatest
and where least?
85. Name the common kinds of stone used in building.
86. Define the terms "quarry-faced," "rough-pointed," "fine-axed,"
"bush-hammered," as applied to the dressing of stone.
87. Describe "rubble" masonry, "ashlar" masonry, and "broken ashlar"
masonry.
88. What are "headers" and "stretchers"?
89. What should be the proportion of "headers" to "stretchers"?
90. How would you prepare the foundation for a heavy wall, and how
deep should it be excavated?
91. How are walls founded on soft or yielding materials?
92. Describe a good quality of bricks, and state how you would know a
good brick from a poor one.
93. In how many ways is brickwork "bonded" to make good work in heavy
walls?
94. What is hydraulic cement, and how many kinds do you know of?
95. Which do you consider the better quality, Rosendale or Portland,
and why?
96. What is mortar composed of, and how mixed?
97. What kind of sand should be used, and how do you test its quality?
98. What is the meaning of the term "setting" as applied to cement?
99. How would you test cement?
100. What is concrete, of what composed, and in what proportion should
its ingredients be mixed?
101. Name the common kinds of wood used in building.
102. What kind of timber resists decay longest under ground?
103. How may timber be preserved from decay?
104. What do you understand by limit of elasticity as applied to a
beam under strain or pressure? What is meant by the neutral axis of a
beam?
105. What is the tensile strength of a good quality of wrought iron
per square inch?
106. For what parts of a structure may cast and wrought iron be used
in reference to tension and compression?
107. Make a sketch of the form of cast-iron beam best adapted to
resist a transverse strain.
* * * * *
CELEBRATION OF THE FIVE HUNDREDTH ANNIVERSARY OF THE UNIVERSITY OF
HEIDELBERG, AUGUST, 1886.
The wave of pleasure and enjoyment which flooded everything has
passed. Heidelberg, usually so quiet, assumed the role of a city of
the world, and all was bustle and excitement in the streets, which
were hung with flags and other decorations. The trains constantly
brought new accessions to the crowd, and gayety and mirth reigned
supreme.
The dedication of the renovated _Aula_ of the University served as a
prelude to the festivities of the week. On this occasion a splendid
flag, embroidered by order of the wives of the faculty of the Academy,
an equally costly cover for the scepter, and a silver inkstand were
added to the treasures of the University. Conspicuous among the
numerous presents received were a richly carved set of furniture--the
gift of former students from Switzerland--and all the publications of
certain book dealers.
On the afternoon of August 2, the Grand Duke and Duchess arrived in
Heidelberg, where they were received with much enthusiasm. They
remained at the modest palace during the time of the jubilee, and
whenever they appeared they were greeted with expressions of
patriotism and love. On the evening of the 2d, the _Oberburgermeister_,
Dr. Wilckens, extended a hearty welcome to the guests who had gathered
in the over crowded hall. Vincenz Lachner conducted the musical part of
the entertainment, which was charming. The German Crown Prince arrived
early on the 3d, so as to accompany his royal cousins to the service in
the beautifully decorated _Heiliggeistkirche_, on which occasion Prof.
Bassermann spoke with great effect. At 11 o'clock, the Court appeared in
the _Aula_, where the Grand Duke presided, in virtue of his office of
"Rector Magnificentissimus." His address was followed by those of the
Crown Prince; the _Prorector Geheimrath_, Dr. Bekker; Edward Zeller, of
Berlin; Jules Zeller, of Paris; and others. In the evening the citizens
and strangers were attracted to the _Jettenbühel_ by the festival at the
castle; from 7:30 until 10 o'clock the nobility held court in the
_Bandhause_. The scene was like fairyland, all the outlines of the
castle were marked by thousands of small lights, and the court was
lighted by great candelabra. In the ever-increasing crowd it was
difficult to find a place and to obtain refreshments, which were given
out in immense quantities by the State.
On the morning of the 4th the people thronged again to the
_Heiliggeistkirche_ to listen to the address of the _Geheimrath_, Dr.
Kuno Fischer, on the fate of the Palatinate and Heidelberg, which was
preceded and followed by music. After this the participants in the
festival were brought together by a dinner in the Museum Hall, and
seldom have speeches so inspired an audience as did those of the Grand
Duke and the Crown Prince. Never has Heidelberg seen such a
torch-light procession as that formed by the students in honor of
their Rector; 3,000 torches lighted him to the City Hall. He thanked
them, and proposed cheers for the Crown Prince.
On the morning of the 5th there was the presentation of degrees. In
the afternoon a special train carried four hundred people to
Karlsruhe, where the royal party held a great reception. The capital
was decorated with flags, the city parks were lighted with Bengal
lights, there was music, and a song by the patriotic bard Vierordt was
sung.
All the splendor and interest shrank into insignificance before the
grand historical procession on the morning of the 6th, which made a
lasting impression on the minds of all. The throng of 100,000 people
watched quietly while the whole history of the Palatinate passed in
review before them. The procession illustrated this history much
better than it could have been told by any professor or any book.
There was not a vacant space to be found, extra trains having brought
more spectators, and yet everything passed off quietly and without
accident. In the evening there was a heavy shower, which freshened
everything, leaving no ill effects to be seen the next morning, which
was more than could be said of many of those who attended the imposing
_Commerse_ of the Heidelberg students. As a former student, the Grand
Duke appeared among the 6,000 visitors at the _Commerse_, where he
presided and spoke enthusiastically of the Emperor. Other speeches
followed, until the conversation became so animated that even Von
Treitschke, who was received with an ovation, could not be heard. At
midnight the court retired and the _Fidelitas_ succeeded to their
rights.
On the 7th the time was spent in excursions and carousing until the
illumination of the castle began. I never saw an illumination of the
ruins which could compare in beauty with that of the 7th. The night
was favorable for fireworks, until finally they were rivaled by the
moon, numerous boats trimmed with colored lanterns passed along the
river, there were fire-wheels on the bridge, water fireworks on the
river, and the quiet was disturbed alternately by the rockets and
music, and when the names of the Grand Duke and Duchess, crowned with
brilliant fire, appeared over the water, there was an involuntary
outburst of enthusiasm. If the old Elector and Electoress could have
been present at the closing entertainment of the jubilee, on the
evening of the 8th, they would have rejoiced to see the new life
brought to the ruins by their successor.--_Illustrirte Zeitung._
* * * * *
MANUFACTURE OF LEATHER IN RUSSIA.
From this extensive paper it appears that the matters chiefly used in
tanning are the bark of the oak, containing from 6.04 to 4.37 per
cent. of tannin according to the season, that of willows, of the elm,
and the birch. The leaves of the arbutus, employed in the governments
of Kasan, Viatka, and Perm, contain about 16 per cent. of tannin,
while the root of wild sorrel (_Rumex acetosella_) contains 12 per
cent. For removing the hair from hides, a lye made from wood ashes is
still employed. The softening of the leather is effected by means of
the excrement of dogs, which acts on the leather by means of the
biliary acid present, which forms with soda a kind of soap. After
tanning, white Russia leather is coated with a mixture of tar and seal
oil. Black Russia leather is dyed with alum, extract of sanders, and
ferrous sulphate. Horse hides are tanned to a great extent for sole
leather.--_M. Ryloff._
* * * * *
IMPURITIES IN PHOTOGRAPHIC CHEMICALS, AND TESTS FOR SAME.
[Table referred to in a paper read before the Birmingham Photographic
Society by G.M. JONES, M.P.S.]
------------------+---------------------+----------------------------------
SUBSTANCE | IMPURITIES | TESTS.
| POSSIBLY PRESENT. |
------------------+---------------------+----------------------------------
Ammonia, | Carbonic acid | Renders lime-water milky.
NH_{3} | |
Molec. Wt. 17 | Dissolved solid | Residue left on evaporation.
| matter |
| |
| Chlorides | After acidulating with nitric acid,
| | it gives a precipitate with silver
| | nitrate, which after washing is
| | readily soluble in ammonia and
| | reprecipitated by nitric acid.
| |
| Sulphates | After acidulating with nitric acid,
| | it gives a precipitate with
| | barium nitrate.
| |
| Lime | A white precipitate with oxalate
| | of ammonium.
| |
| Lead is often | Black precipitate with sulphureted
| present, derived | hydrogen.
| from the action |
| upon flint glass |
| bottles |
| |
Nitric acid. | Traces of | After dilution it gives a
H, NO_{3} | sulphuric acid | precipitate with barium nitrate.
Molec. Wt. 63 | |
| Chlorides | After dilution it gives a
| | precipitate with silver nitrate.
| |
| Peroxide of nitrogen| The acid is yellow.
| |
| Iodine may be | After dilution and cooling it gives
| present if the acid | a blue color with starch, paste,
| be prepared from | or mucilage.
| sodium nitrate |
| |
Hydrochloric | Free chlorine | Liberates iodine from solution
acid, HCl | | of potassium iodide. See also
Molec. Wt. 36.5 | | "Chlorides," nitric acid.
| |
| Sulphuric acid | As above for nitric acid.
| |
| Perchloride of iron | Yellow color. Brown precipitate
| | with ammonia added till it
| | smells slightly.
| |
Sulphuric acid, | Bisulphate of | Residue on evaporation.
H_{2}SO_{4} | potassium |
Molec. Wt. 98 | |
| Sulphate of lead | Milkiness on dilution. May be
| | completely freed from lead by
| | diluting with three or four times
| | as much water, and allowing
| | to settle.
| |
Acetic acid | Water | Does not solidify when cooled
(glacial), | | to 17° C. (53º F.)
H C_{2}H_{3}O_{2} | |
Molec. Wt. 60 | Sulphurous and | White precipitates with silver
| hydrochloric | nitrate.
| acids |
| |
| Aldehyde, or | Blackens in the light after adding
| volatile tarry | silver nitrate.
| matter |
| |
| Organic sulphuric | Smell of garlic.
| acid |
| |
Citric acid, | Tartaric acid | Strong solution of potassium.
H_{3}C_{6} | | Acetate added to a strong solution
H_{5}O_{7}H_{2}O | | of the acid will deposit white
Molec. Wt. 210 | | crystalline bitartrate.
| |
Pyrogallic acid | Metagallic acid | Black residue, insoluble in water.
(C_{6}H_{3})HO_{3}| |
Molec. Wt. 126 | |
| |
Silver nitrate, | Free nitric acid | Reddens litmus paper. (Neutral
AgNO_{3} | | silver nitrate does not
Molec. Wt. 170 | | affect litmus.)
| |
Potassium | Chlorides and | Same as for ammonia.
carbonate | sulphates |
K_{2}CO_{3} | |
Molec. Wt. 138 | |
| |
Potassium | Potassium carbonate| A strong solution is alkaline to
iodide, KI | | test paper.
Molec. Wt. 166 | |
| Sulphates and | Same as for ammonia.
| chlorides |
| |
| Potassium iodate | A pretty strong solution becomes
| | yellow from liberation of iodine
| | on addition of dilute sulphuric
| | acid or, better, a strong solution
| | of citric acid.
| |
Potassium | Similar to | See potassium iodide.
bromide, KBr | potassium iodide |
Molec. Wt. 119 | |
| |
Sodium carbonate, | Chlorides and | Same as for ammonia.
Na_{2}CO_{3} | sulphates |
Molec. Wt. 106 | |
| |
Sodium chloride, | Chloride of calcium | Oxalate of ammonium (after
NaCl | Chloride of | addition of a little acetic acid)
Molec. Wt. 58.5 | magnesium | gives a milkiness, or precipitate,
| | indicating calcium; filter this
| | out and add ammonia, chloride of
| | ammonium, and phosphate of sodium
| | (clear solutions). A precipitate
| | indicates magnesium. Both the above
| | cause dampness in wet weather.
| |
| Sodium sulphate | As for "sulphates" in ammonia.
| |
Potassium | Potassium carbonate | Effervescence with dilute acids,
cyanide, KCN | nearly always | giving off a gas carbonic
Molec. Wt. 65, | present | anhydride, which renders
and hydrate, KHO | | lime-water turbid.
Molec. Wt. 56 | |
Kaolin | Chalk | Effervescence with dilute acids.
| |
Water, | Sulphates and | Same as for ammonia.
H_{2}O | chlorides |
Molec. Wt. 18 | |
| Calcium carbonate, | Deposited by boiling. Test as
| temporary hardness | for calcium chloride. See
| | sodium chloride.
| |
| Ammonia, almost | Brown coloration, or
| always present in | precipitate with Nessler's
| distilled and rain | reagent.
| water |
| |
Gelatine | Alum | Ash, sometimes as much as ten
| | per cent.
| |
| Fatty matter | Separated by precipitation with
| | alcohol. Dissolved out by ether
| | or benzine, and left as a residue
| | on evaporation of the solvent.
| |
| |
Ammonium bromide | Potassium bro- | Leaves a residue when heated.
(NH_{4})Br | mide or other |
Molec. Wt. 98 | non-volatile |
| bodies |
| |
| Ammonium chloride | Same as for chlorides in
| | ammonia.
| |
Pyrogallic acid | Powdered glass | Left behind on solution.
| |
Potassium iodide | Potassium bromide | The crystals of bromide are
| | usually more transparent than
| | those of iodide, but no reliance
| | can be placed on this.
| |
Silver nitrate | Potassium nitrate, | Will not yield the full quantity
| sometimes present | of chloride on precipitation
| in the fused | with HCl. Gives a purple color to
| sticks--not in | flame.
| the crystals |
| |
Sulphuric acid | When vended as pure,| No easy test can be given, as the
| it invariably | substances are so numerous some of
| contains a trace of | them volatile, and most require
| iron. Common acid is| separation from the acid before
| also liable to | detection.
| contain arsenic, |
| selenium, thalium, |
| and many other |
| substances. |
| |
| Organic matter, as | Gives a brown color to the acid.
| a piece of straw |
| in a carboy of acid |
| |
Hydrochloric acid | Arsenic | Marsh's test.
| |
| Some yellow samples | Reinsh's test; a small piece of
| contain no iron, | copper foil becomes coated
| but an organic salt,| on boiling in dilute acid.
| and give an alkaline|
| ash on ignition of |
| the residue after |
| evaporation |
| |
Calcium chloride | Calcium hydrate | The clear filtered solution made
| | with distilled water is alkaline
| | to test paper, and gives a
| | precipitate on breathing into it
| | through a tube.
| |
Pure (?) chemicals| Broken glass, bits | These impurities either float or
generally | of straw, wood, | sink on solution, and may easily
| paper, etc. | be seen.
-------------------------------------------------------------------------
G.M. JONES, M.P.S.
* * * * *
THE CATASTROPHE AT CHANCELADE.
The Chancelade quarries near Perigneux, which caved in Oct. 22, 1885,
under circumstances that are still fresh in the minds of all, have
gained a celebrity that renders it unnecessary for us to revert to the
details of the catastrophe. It will suffice to recall the fact that
after the accident a private committee was formed for the purpose of
making an attempt to save the five victims who had been surprised in
the drifts, and who happened to be in the bottom levels.
[Illustration: FIG. 1.--PHOTOGRAPHIC EXPLORING APPARATUS.]
The Lippmann establishment at once offered to make a boring by means
of which it would be possible to communicate with the galleries in
which the men were imprisoned, but, despite the most active efforts,
success was found impossible. In order to satisfy public opinion, the
committee resolved to bore a well 12 inches in diameter to a depth of
23 feet, that should permit of reaching the gallery; but this did not
render the latter accessible. How was it to be seen what had occurred,
how was it to be made certain that the men were dead, and that all
hope of rescue must be abandoned? To Mr. Langlois, a Parisian
photographer, was confided an order to construct a special apparatus
which might be let down to the bottom of the well by a cord, and
which, being capable of operating from a distance, should furnish the
required information through sensitized plates. As may be seen, this
operation presented peculiar difficulties, although Mr. Langlois was
enabled to overcome these with much skill.
The photographic apparatus that the ingenious operator constructed was
contained in a metallic case that could be let down into the bore
hole. The upper and lower parts of the contrivance were provided with
incandescent lamps, that could be lighted or extinguished from a
distance, by means of conductors. The photographic apparatus, properly
so called, formed of an objective and camera with its sensitized
plate, was inclosed in a cylinder 3½ inches in diameter. By means of a
cord drawn at the mouth of the well, the apparatus could be made to
issue from its vertical sheath, and to pivot around its axis so as
take views in different directions (Fig. 1).
The entire affair was suspended by twelve-foot iron rods, connected
with each other end for end.
In using the apparatus, the operating was done in a shanty, which
served as a dark room. The device was let down into the bore well
until it touched bottom. At this moment a cord was pulled so as to
raise the camera, and then a few moments were allowed to elapse in
order that the apparatus might become immovable. As the objective was
all the time in the dark, it had neither cap nor shutter, but was
unmasked from the beginning of the operation.
In order to form an impression on the plate, it was only necessary to
give light; this being easily done by passing an electric current by
means of a commutator, so as to light the incandescent lamps. At the
end of the exposure, the lamps were extinguished and the entire
apparatus was immersed in darkness. The mean time of exposure was from
four to five minutes. The apparatus was then hauled up, and the
negative developed.
The experiments could be renewed as often as necessary, and the
apparatus be pointed in all directions by turning it a certain number
of degrees by means of a lever attached to the upper rod. In this way
were obtained various views of the inaccessible gallery in different
planes.
[Illustration: FIGS. 2 AND 3.--REPRODUCTION OF PHOTOGRAPHS TAKEN IN
THE INACCESSIBLE GALLERIES.]
We reproduce herewith two of Mr. Langlois' most interesting
photographs. One of these shows the head of the corpse of a young
miner whose face stands out in relief against the side of the gallery
(Fig. 2) the other shows a wheel and a lot of debris heaped up
pell-mell (Fig. 3).
The series of proofs obtained from small negatives, two inches square,
gave the completest sort of information in regard to the aspect of the
subterranean gallery.
The exact place where the boring had been done and the entire and
broken pillars were recognized, as was also the presence of two
corpses, thus showing that it was indeed here that it would have been
necessary to act in order to render aid to the unfortunates.
[Illustration: FIG. 4.--FAULT THAT CAUSED THE ACCIDENT.]
In Fig. 4 is shown the appearance of the great fault that caused the
accident at Chancelade. It seems to us that this method of
photographing inaccessible subterranean galleries ought to receive
numerous applications in the future.--_La Nature._
* * * * *
SOMZEE'S NEW GAS-BURNERS.
With the object of effecting a very intimate mixture of gas and air,
and of causing this mixture to reach the point of ignition at as high
a temperature as possible, M. Leon Somzee, of Brussels, has designed
several new forms of gas burner, which we now proceed to describe and
illustrate, from particulars and by drawings kindly supplied by an
esteemed Brussels correspondent.
The high-power burner shown in Fig. 1 effects perfect combustion of
the heated mixture of air and gas, which is introduced by the draught
determined by the arrangement. What chiefly distinguishes this burner
from others of its class is the fact that it is perfectly suited to
domestic lighting--that is to say, it may be arranged for a
comparatively small consumption of gas, while giving an increase of
250 per cent. of light.
[Illustration: FIG. 1. and FIG. 2. INCANDESCENT AND HIGH-POWER
BURNERS.]
The burner proper is a cage or basket of specially prepared magnesia,
which yields a warmer tone of light than any obtained hitherto, while
not requiring so high a temperature before combustion. The cap, made
of a fire-resisting substance, fits on to a tubular arrangement, R,
fixed in the upper portion of the body of the burner. The latter is
supplied by air entering at the cone, O, which terminates the inner
chamber, K, of the heater, and also by that drawn in by the rising
column of gas, passing before the orifices, D, which may be regulated
at will. The small burner, I, which is kept constantly alight, heats
the central compartment, K, the sides of which transmit heat to the
gas circulating in the annular casing, L, of the compartment. The
heated gas passes, by the passage, AA¹, into the space, C, where it
becomes intimately mixed with the air entering at OP, and also with
the outer air arriving by the lateral apertures, D.
The _vis viva_ of the jet is diffused through this mixture, which thus
becomes very intimate, when it penetrates into the tubular
arrangement, R; combustion now taking place at the top, while the
refractory cap emits a bright orange light of great steadiness. As it
is not the flow of gas which determines the entrance of the outer air,
the former may be used at any pressure--an advantageous arrangement in
all respects.
When the small burner, I, in the lower chamber is lighted, the
products of combustion issue by the orifice, O, of the compartment,
terminating in a needle like that of the steam injector; and the jet
draws along the air entering the apertures, PP, above the cone. The
gas from the pipe, arriving from the annular space, L, fills the two
lateral pockets shown in dotted lines, and passes through the
orifices, AA¹, which communicate with the upper chamber of the
burner. The manner in which it is conveyed thence to the tubular
arrangement has already been described.
Fig. 2 shows a more simple method of carrying out the same principle,
and of effecting a considerable saving in gas for a given intensity of
light. In this form, a wick, T, impregnated with an alkaline earthy
solution, a few seconds after lighting, affords a focus of white light
remarkable for its steadiness and brilliancy. A draught of air is
created by a jet of gas issuing from the hollow needle, B, and passing
through the vessel, D, which is provided with orifices, O, for the
entrance of air. The air and gas pass from D into C, whence (after
their intimate mixture is effected) they pass into the tubular
arrangement, F, at the top of which combustion takes place.
To regulate the proportions in which the air and gas should mingle, in
order that the combination should be as intimate as possible, the air
inlet is made variable by a perforated collar, which permits of the
orifices, O, being more or less covered. The other proportions of the
burner--that is to say, the relative capacity of the two compartments
and the length of the hollow needle--are determined by the sectional
area of the supply-pipe for the gas, which is admitted under moderate
pressure. Instead of a wire-gauze cap, impregnated with a solution of
metals or of salts, two fine platinum wires may be used--one bent into
the form of a semicircle of about an inch radius, and the other (of
slightly larger diameter) rolled spirally round the former. When both
ends of the two wires are connected with the upper portion of the
tubular arrangement (which in this case is flattened), and the gas is
ignited at the burner, the metallic arc becomes red hot, and then
brightly incandescent, emitting a light, less brilliant indeed than
with magnesia, but of remarkable steadiness.
In this case the production of light is chiefly due to the fact that
calorific condensation, caused by the use of the helicoidal coil
surrounding the curved wire, prevents loss of heat in this conductor.
In these forms of high-power burner, in which the gas is used directly
for the production of light, the difficulty generally encountered of
heating the air (present in a larger volume than the gas) has been
successfully overcome.
Fig. 3 shows the straight and outspread flame burner with a special
heater. In this arrangement the gas and air are heated before
combustion, in the compartment, G, directly exposed to the action of a
small Bunsen burner, R, which is placed (in an opaque glass) in the
middle of a lyre-shaped figure formed by the two gas-pipes, AA. The
burner proper consists of two fine annular passages meeting above, and
emitting a thin annular sheet of gas over the guide, T, made of a
white refractory substance placed between the two annular jets. The
object of this guide is to stretch the incandescent sheet of flame,
composed of several jets, and interpose friction, so as to prevent a
too rapid ascent of hot gases.
[Illustration: FIG. 3 and FIG. 4 REGENERATIVE BURNERS WITH INVERTED
FLAMES.]
The luminous focus is placed within a glass globe, C, mounted on the
bell, B, of the heater; and the external air enters this bell,
mingling with the products of combustion of the heating burner, R. The
portion, D, of the annular passage, B, being made of a highly
conductive metal, the gas becomes heated in passing to the burner, so
that both gas and air are raised to the same temperature by the time
they reach the orifices of the burner. Instead of prolonging the
gas-pipe to the point of bifurcation, a chamber may be arranged
immediately below the guide, for the gas and air to become intimately
mixed by passing through several perforations or wire gauze, receiving
the excess of heat from the white porcelain guide. The admission of
gas to both the main and heating burners is regulated by a double
valve in the pipe; but this arrangement may be used without any
previous heating of the gas and air.
Fig. 4 shows a similar arrangement to that above described, but
reversed; the gas and air being previously heated by the products of
combustion. The two pipes, D, lead the gas to the burner; and the
incandescent sheet of flame is drawn over a white refractory
substance, having in its center an orifice through which the hot gases
rise to the upper portion of the burner. The luminous sheet is spread
out all the better on account of this return of the flames, which also
causes the mixture of air and gas to be more complete than when they
rise directly. The gas escapes horizontally from the orifices of the
annular burner, B, and mingles with the double current of hot air
which rushes in above the flame inside the globe, and also below
through the central portion of the burner.
This lamp throws its light vertically downward; and its illuminating
power may be increased by providing, above the incandescent sheet, a
reflector, which diverts into a useful direction the rays thrown
toward the ceiling. In this arrangement of lamp the flame is
excessively condensed by its being turned back over the refractory
guide; and this condensation greatly favors the production of light.
On the other hand, the combustion of the gas is very perfect, because
the currents of hot air are thrown directly upon the two sides of the
flame; and thus the reciprocal action becomes more intense. Lastly,
the division of the gas into a large number of small jets, in contact
with which the hot air forms an intimate mixture, causes a greater
quantity of molecules to partake in the combinations; thus affording a
proportionate increase of temperature in a given space and time.
[Illustration: FIG. 5. REGENERATIVE BURNER WITH FLAME DEFLECTED
OUTWARD.]
Owing to these various circumstances, the final effective duty of this
burner is advantageous, so that it yields an illuminating power which
may be put at from 200 to 250 per cent. above that of ordinary
burners, and about 25 per cent. more than that of other regenerative
burners. The flame is comparatively steady; the loss due to the
friction over the white porcelain being almost eliminated, because the
flame only presses upon the guide for a small portion of its surface,
and is only spread out to the extent of its dark zone.
The contact between the incandescent sheet of flame and the guide may
be made as short as desired, and the motion of the gaseous mass be
directed by a simple button placed in the center of the burner; thus
giving the form shown by Fig. 5, which, however, differs from the
previous figure in the fact that the inverted flame is directed
outward instead of inward.
In this arrangement the button, T, is fixed in the middle of the
burner, which is made cylindrical and annular, or may consist of a
ring of small tubes, to which the gas is led by a single pipe; leaving
the whole "furnace" free for the circulation of air and the products
of combustion. This is the most recent development of the principle
patented by M. Somzee in 1882, viz., the formation of an illuminating
sheet of flame, spread out laterally, while heating the gas and air by
the products of combustion.
Figs. 6 and 7 show two forms of burner designed especially to give
economical results with a small consumption of gas. The former is an
ordinary Argand burner in which hot air is introduced into the upper
portion of the flame, so as to increase the activity of combustion.
The luminous sheet of flame is then spread out by a metal disk
attached to the end of the tube, D, which introduces the air into the
flame. The outer air becomes heated in its passage through the wire
gauze, T, which absorbs the heat liberated in the interior of the
apparatus, and also that which is radiated from the incandescent sheet
and reflected by a metal shield, P, surrounding the dark part of the
flame.
[Illustration: FIG. 6. FIG. 7. TYPES OF ECONOMICAL BURNERS.]
It is the combustion of gas, without the production of useful luminous
effect inside the shield, which supplies the reflected as well as
radiated heat to the air. The temperature is still further increased
by the heat transmitted to the metal portion of the burner, and
absorbed by the wire gauze, between the close meshes of which the air
from outside is forced to circulate. Air is admitted inside the flame
by the chimney, D, placed above the focus, and in which it is raised
to a high temperature by friction on the upper part of the lamp glass,
at E, and afterward by its passage through the horizontal portion of
the bent tube. This tube is impinged upon on the outside by the
flames, and also by the products of combustion, so that it forms a
veritable heater of the currents which traverse it.
The introduction of hot air into the central portion of the sheet of
flame is advantageously supplemented by the spreading out of the flame
by means of the metal disk, without any possibility of its being
divided. In this way a more intense heat is obtained, and consequently
the illuminating power is considerably increased, by the uncombined
carbon being more readily set free, and being thus kept longer in the
flame, F. This burner, which may be constructed for a moderate gas
consumption, gives remarkable results as regards illuminating power
and steadiness; the abstraction of heat in no way impairing the
luminosity of the flame, which preserves all its brightness.
The Argand burner with double chimney, shown in Fig. 7, is also an
economical one for a small consumption of gas. The air admitted to
both the inside and the outside is raised to a high temperature by
passing along the spirals of a second and transparent chimney, C¹,
which surrounds the cylindrical glass, C. The gas itself is heated by
passing through this hot chamber before reaching the outlet orifices;
so that the mixture of air and gas takes place under the most
favorable conditions for their perfect combustion.
The burner is an ordinary Argand, which may terminate below in a small
chamber for the gas and air to mingle. But this is not necessary; and
the usual arrangement for mixing the air and gas may be adopted. The
outer air enters at the top of the central chimney, C and passes into
the annular space between the two glasses; then descends by the two
spiral passages, which surround the cylindrical glass and terminate
in a portion hermetically sealed by a brass plate attached to the
supply-pipe. All the parts of the burner are thus surrounded by a
highly-heated atmosphere, especially at the bottom of the double
chimney; and it will be readily understood that, if the branches which
lead the gas to the burner are constructed of a highly conductive
metal, the gas will become heated in its turn by passing through
passages raised to a high temperature.
The elements are therefore dissociated or separated before their final
combination; thereby raising the calorific and luminous effect to the
highest possible degree. Such a burner can, of course, be made as
small as may be required; thus lending itself admirably to the
subdivision of illumination. The only precaution required is to
properly proportion the sectional area of the hot-air passages to the
radiant surface of the flame, so that the heat does not become too
intense at the lower portion of the burner.
Fig. 8 shows a double flame burner on the principle of Mr. Heron's,
but with admission of hot air into the angle formed by the flames. As
exemplified by Mr. Heron, if two equal batswing burners separately
give a certain amount of light, on the two flames being brought into
contact, so as to form a single flame, the luminosity is considerably
increased, owing to the condensation of heat which results from their
meeting. The two incandescent sheets are, as it were, forced into one
another, so as to be combined.
[Illustration: FIG. 8. DOUBLE FLAT-FLAME BURNER]
The high-power burners of Douglass, Coze, Mallet, and others were
designed on this principle; but its application to uninclosed burners
was not very satisfactory, because the great cooling down of the inner
surface of the flames by the strong draught of cold air impaired their
illuminating power. To counteract this difficulty, M. Somzee adopts a
heating burner, A, which he places between the two batswing burners,
B, so that the products of combustion rise in the angle made by the
two lighting flames, as shown; thus greatly increasing their
luminosity while maintaining a low consumption of gas.
M. Somzee also raises the illuminating power of an ordinary flat-flame
burner by causing an obscure effluvium to traverse the dark portion of
the flame. The effect of this is to increase the activity of
decomposition in this portion, so that the particles of carbon are the
more readily set free, and remain longer in suspension in the luminous
zone. The obscure effluvium may be determined between two points by
the electric current, or be caused by the heating of an imperfect
conductor by the current; or, again, it may result from a metal
conductor heated by the reactions produced in the middle of the flame,
by separating the cone of matter in ignition. The effect may be
compared with that obtained by the concentration of two sheets of
flame; but in this case the sheets are formed by the constituent parts
of one and the same flame, whence results a more complete utilization
of the elements composing it. This system is, in fact, a
simplification of the arrangement adopted in the double-flame burner
seen in Fig. 8.
Fig. 9 shows a reflecting and regenerative burner with double glass.
The crown, made of metal polished on both sides, has a circular
groove, G, for receiving the end of the central chimney, C, and
presenting an annular aperture by which the products of combustion
enter. The second glass, C¹, is fastened to the collar of the
burner carrier, and does not come into contact with the metal crown;
so as to allow the air to enter from outside for supplying the burner.
The gas enters by the pipe, T, provided with a cock. This pipe is
continued to the top of the apparatus, and there spreads out into the
form of a dome; thus dividing into two compartments the trunconic
chamber, S¹ S², whence the hot gas returns to the body of the burner,
B.
[Illustration: FIG 9. REFLECTING AND REGENERATING BURNER.]
On the burner being lighted from below, the products of combustion
rise in the inner chimney, and enter the heater, which they traverse
through its entire extent, while impinging against the outside of the
gas reservoir, to which they give up a large portion of their heat.
They then pass by the passage, D, into the atmosphere or into a
chimney. The air necessary for combustion enters at the top of the
outer globe, and becomes highly heated in its passage through the
space comprised between the two glasses of the burner. In this way it
reaches the burner, and forms an intimate mixture with the small jets
of gas which compose the flame. The gas, on leaving the supply-pipe,
T, fills one of the compartments, S¹ S², of the heater, and then
returns by the second compartment, and again descends by the casing of
the supply-pipe, having its temperature still further raised by
contact with the internal radiation of the flame.
Under these conditions, all the parts of the burner are supplied by
heated air, and the combustion becomes very active; thus increasing
the intensity of the flame, and consequently that of the light
afforded, while at the same time effecting a saving of 50 per cent. of
gas. This burner may be made of any size, and for consumptions not
exceeding that of an ordinary Argand. In fact, the gas is consumed at
a low pressure, escaping with no greater force than that due to the
heat of the products of combustion. It is sufficiently expanded on
coming into contact with the current of hot air, the activity of which
is regulated by the height of the apparatus, that is to say, by that
of its two chimneys. The mixture is made in such proportion as to
obtain from the gas and air as great a degree of luminosity as
possible. The high temperature of the gas, and the independent means
of heating the air and gas, constitute the essential principles of
this burner.--_Journal of Gas Lighting._
* * * * *
THE CLAMOND GAS BURNER.
[Illustration: THE CLAMOND GAS BURNER.]
In this burner, which is a French invention, the light is produced by
burning ordinary coal gas within a basket of magnesia, which is
thereby brought to a high state of incandescence, and from which a
white, steady light is radiated. It may be said to consist of three
different parts. The first and inner part is a central column, B, of
fireproof material. The second part consists of two concentric
cylinders placed round the inner column and communicating one with the
other through the cross cuts, J. The third part is a china cup
inclosing the other parts, and perforated with a number of holes. The
gas burns in two different places. From A it passes directly through
B, at the top of which it branches off through tubes to an annular
chamber, D, from which it escapes through the openings, _a_, _a_, _a_,
where combustion takes place. The other combustion occurs within the
circular space, G, I, between the column and the inner of the two
surrounding cylinders, through two channels, E E, in the lower part of
the central column. The gas passes into a circular chamber, F F, and
escapes through small holes in the upper partition of this chamber,
where it burns. The product of this combustion passes put into K,
through the cross cuts, J. The air entering through the holes, H L, of
the outer china cup passes along the inner of the two concentric
cylinders, which is heated to redness, and rises highly heated toward
the upper annular burner, where the gas burns at _a_, _a_, _a_, in small
separate flames, each entirely surrounded by the hot air. This insures
perfect combustion of the gas within the basket of magnesia placed
above, and which is thus brought to a state of incandescence. It will
be seen from this description how simple and practical the
arrangement is. It is claimed for the light produced that it will
stand comparison with the electric light. Like that, it shows colors
perfectly true, and will enable an observer to distinguish between the
most delicate shades, allowing of the finest work being executed as by
daylight. It is, moreover, stated to be perfectly steady. As the
Clamond burner can be fixed to any gas bracket or lamp now in use, its
adoption causes no other expense than the cost of the burner itself.
There is no expensive installation, and when used in combination with
the electric light, it is claimed that a uniform lighting will be
obtainable instead of the unpleasant contrast between gas and
electricity. Another important advantage obtained by the Clamond
burner is the saving effected in the consumption of gas as compared
with the same power of light obtained from ordinary burners.
* * * * *
A NEW THERMO-REGULATOR.
In the thermo-regulators which have been constructed heretofore, the
heat has been regulated by the variation in the inflow of gas to the
heating flame. The apparatus described below, and shown in the
accompanying cut, taken from the _Zeitschrift fur Instrumentenkunde_,
operates on an entirely different principle. The distillation and
condensation process of a fluid heated to the boiling point in the
vessel, A, is as follows:
[Illustration]
The steam passes first through the pipes, _a_ and _c_, into the
serpentine tube, where it is condensed, and then flows through the
tubes, _d_ and _b_, back into the vessel, A, if the cock, _r_, is
closed, but if the said cock is open, it flows into the receptacle, K.
When the liquid begins to boil the steam passes freely through the
tubes, _d_ and _b_, part passing through the tube, _f_, out into the
air, and the other part passing through the open cock, _r_, to the
receptacle, K; but the condensed liquid soon closes these passages to
the steam. At _h_ is an opening for a thermometer, _t_, and through
this opening the liquid can be poured into the vessel, A. If the cock,
_r_, is kept closed, the volume of liquid in the vessel, A, cannot be
diminished, and the bath, B, must take the constant and uniform
temperature of the steam in the vessel, A, as the vessel, B, is heated
evenly on all sides.
This apparatus can also be used as an air bath, in which case the
vessel, B, is left empty and closed by a suitable stopper.
* * * * *
PIPETTE FOR TAKING THE DENSITY OF LIQUIDS.
The accompanying engraving represents a simple apparatus, which any
person accustomed to working glass can make for himself, and which
permits of quickly, and with close approximation, estimating the
density of a liquid. In addition, it has the advantage of requiring
but a very small quantity of the liquid.
It consists simply of a straight pipette, A B, to which is affixed
laterally, at the upper part, a small U-shaped water gauge.
The two branches of the gauge, as well as the pipette itself, are
graduated into equal divisions. If need be, the graduating may be done
by simply pasting on the glass strips of paper, upon which a graduated
scale has been drawn. The zero of the pipette's graduation is exactly
at the lower extremity, B. The graduation of the two gauge tubes
extends in both directions from a zero situated near the center. The
zeros of the two branches must correspond as exactly as possible, so
that they shall be in the same horizontal plane when the apparatus is
fixed upon a support. To render the apparatus complete, it only
remains to adapt, at A, a rubber tube provided with a wire clamp, and
terminating in a short glass tube for sucking through with the mouth.
[Illustration: PIPETTE FOR TAKING THE DENSITY OF LIQUIDS.]
For taking the density of a liquid, we plunge the end, B, into it, and
then suck, and afterward close the rubber tube with the clamp. It is
essential that this latter shall hold well, so that the levels may
remain constant.
We now do the reading. Suppose, for example, we read 250.3 mm. on the
pipette, and 147.7 mm. and 152 mm. on the branches of the gauge.
Having these data, we loosen the clamp, and allow the liquid to flow.
On account of capillarity, there remains a drop in B; and of this we
read the height, say 6 mm. A height 250.5 mm - 6 = 244.5 mm. of liquid
raised is, then, balanced by a column of water of 147.5 + 152 = 299
mm.
Now the heights of these two liquids is in the inverse ratio of their
densities:
_d_ 299.5
--- = -----, whence _d_ = 1.22.
1 244.5
We obtain _d_ by a simple division.
When the instrument has been carefully graduated, and has been
constructed by an expert, the accuracy of the first two decimals may
be relied upon. With a little practice in estimating the last drop, we
may, in trying to estimate the density of water, even reach a closer
approximation. In order to measure the height of the drop accurately,
one should read the maximum height to which the liquid rises between
the fall of two drops at the moment when the last ones are falling,
since at that moment, and only at that, can it be ascertained that the
lower level of the bubble is plane. The error in such reading does not
reach half a millimeter, and, as a suitable height of the apparatus
permits of having columns that vary between 13 and 30 centimeters, an
error of this kind is but 1-300. This is the limit of precision of the
method.
The clamp might be advantageously replaced by a glass cock, or, better
still, A might terminate in a rubber bulb; and a lateral tubulure
might be fixed to the pipette, and be closed with a rubber stopper.
This little apparatus is more easily maneuvered than any of those that
have hitherto been devised upon the same principle. It is capable also
of replacing areometers in ordinary determinations, since it permits
of correcting the error in capillarity that is neglected in
instruments; and, moreover, one can, when he desires to, easily verify
for himself the accuracy of the graduation.--_La Nature._
* * * * *
USEFUL BAGS, AND HOW TO MAKE THEM.
By JOHN T. HUMPHREY.
Since the papers on "Boot and Shoemaking," in vol. i. of _Amateur
Work_, illustrated, I think nothing relating to the leather trades has
appeared in it; and as there must be many among the readers of this
magazine who have a desire to dive deeper into the art of manipulating
leather into the various articles of utility made from that material,
I will endeavor in the series of articles of which this is the
commencement to furnish them with the necessary instructions which
will enable them to do for themselves many things which now are left
undone, or else have to be conveyed miles to some town where the
particular business, or something akin to it, is carried on. To the
colonist and those who live in out-of-the-way districts, it must be a
matter of great regret to observe articles of use, where the material
is in good condition, rapidly becoming useless owing to the inability
of the possessor to do the necessary repairs. Again, it may be that
the article is completely worn out, and the old proverb that "a stitch
in time saves nine," will not be advantageously applied if carried
out. In that case a knowledge of making new what we require, whether
in order to replace something already worn out or as an addition to
our store, must prove beneficial to the thrifty amateur. My object in
writing these articles is not to deprive the mechanic of any portion
of his legitimate occupation, but to assist those who live at a
distance too great to be able to employ him, and who necessarily
prefer any makeshift to the inconvenience of sending miles, and being
without for days, an article which might possibly be set right in an
hour or two.
HOW TO MAKE BAGS.
The old-fashioned carpet bag (Fig. 1) is still unsurpassed by any,
where rough wear is the principal thing to be studied. Such a bag, if
constructed of good Brussels carpeting and unquestionable workmanship,
will last a lifetime, provided always that a substantial frame is
used.
[Illustration: FIG 1.--THE CARPET BAG.]
Next in order comes the brief bag (Fig. 2), more extensively used than
any other. For business purposes it is in great favor with bag users,
being made in a variety of shapes, but all belonging to the same
class. Here we have the shallow brief, deep brief, eclipse wide mouth,
imperial wide mouth, excelsior, courier, and many others; but to know
how to make one will be sufficient for all, the only difference being
in the cut or style in which they are constructed.
[Illustration: FIG. 2.--THE BRIEF BAG.]
The cricket bat bag (represented in Fig. 3) is made on the same
principle throughout as the carpet bag.
[Illustration: FIG. 3.--THE CRICKET BAT BAG.]
Frames and all necessary fittings required in making bags may be
purchased of dealers.
Care must be observed in choosing all the pieces necessary for a bag
from the same pattern carpet, otherwise it will present an unsightly
appearance when completed. There may be some who would prefer American
cloth; this is thoroughly waterproof, and has a good appearance for
some time, but, like all articles of imitation, it has only
_cheapness_ to recommend it. If cloth is to be used (I mean American
cloth), let it be the best that can be bought, that which is called
"double-twill duck," if possible. As the making is the same whether
cloth or carpet be used, it will be understood that the instructions
for making apply to both.
The following tools, which are few and inexpensive, will be required:
A pair of clams (Fig. 4), cost 1s. 6d.; knife (Fig. 5), 6d.; half
dozen awl blades, ½d. each; three or four boxwood handles, 1½d. each;
3 foot rule, 1s.; hammer, 1s.; a packet of harness needles, size 4,
cost 2½d. (these have blunt points); a bone (Fig. 6) will also be
required for rubbing the stiffening into place, cost about 3d.; and a
ball each of hemp and wax for making the sewing threads--hemp 2½d.,
wax ½d. For making holes in the bottom where the nails or studs are
fixed, a large sewing-awl will be required; this will probably have to
be bought at a saddler's; the other tools can all be obtained at any
grindery and leather seller's.
[Illustration: FIG. 4--Pair of Clams. FIG. 5--Knife. FIG. 6--Bone
Rubber. FIG. 7--Method of Measuring Registered Frame: A to A, Top of
Sides; A to B, Top of Gussets. FIG. 8--Pattern of Bottom, Showing
Place of Nails. FIG. 9--Side Pattern Folded. FIG. 10--Gusset Pattern
Folded. FIG. 11--Pattern for Gusset Stiffening. FIG. 12--Handle,
Showing Distance of Rings.]
The awl blades mentioned above are of two kinds, and either may be
used for this work. Those generally used are of a straight diagonal
shape, making a perforation the shape of a diamond, <>*; the others are
perfectly round, tapering gradually to a fine point. To fix them in
the boxwood handles, place the blade in a vise, leaving the unpolished
part above the jaws; hold the handle above this, and commence driving
it down, taking care that the blade is penetrating the middle of the
handle. Continue tapping the handle until the ferrule reaches the
polished part of the blade; it will then be in far enough.
* Transcriber's Note: Original diamond vertical instead of horizontal.
A good serviceable pair of clams may be made by taking two staves of a
good-sized barrel, and cutting about 10 inches off the end of each.
Screw together with three screws (as in Fig. 4), and shape the
uppermost ends so that the outsides meet in a sharp ridge along the
top; this will give a flat surface within the mouth, by which a hold
of the work may be obtained. A two-inch screw will be long enough for
the bottom, which must be turned in as tightly as possible; the others
must not be less than 3 inches, as there will be a space of 1½ or two
inches between the staves at the part where they are inserted. Screw
these just tight enough to give a good sharp spring to the mouth of
the clams when they are pressed open; this will insure the work being
held firmly while being sewn. Sandpaper them over to give a smooth
appearance, and these will be found as useful as bought ones.
A piece of basil leather will be required for the bottom and welts of
the bag. This may be purchased at a leather seller's with the tools.
Cut out the bottom first; the welts may be cut from any narrow pieces.
These must be cut seven-eighths of an inch wide, then folded over, and
lightly hammered down. This brings the two edges together, and when
placed in position, they should lie evenly between the edges of the
material. A piece of string may be laid in the welt to give it a
fuller appearance if the leather is very thin.
The following dimensions of bags when made up will enable the maker to
choose the most useful size:
No. 1, 16 by 14 inches; No. 2, 19 by 16 inches;
No. 3, 21 by 17 inches; No. 4, 24 by 18 inches.
The sizes of frames and parts when cut will be as follows:
Frame. Sides. Bottom. Gussets.
No. 1, 15 inches 16½ by 15½ 16½ by 5½ 15½ by 5½
No. 2, 18 inches 19½ by 17½ 19½ by 6 17 by 6
No. 3, 20 inches 21½ by 18½ 21½ by 6½ 18½ by 6½
No. 4, 23 inches 24½ by 19½ 24½ by 6½ 19½ by 6½
Taking No. 1, 16½ inches will be the length of sides and 15½ inches
the depth. The gussets are also 15½ deep, the width being 5½, the same
as the bottom. Take 1½ inches from the depth of these to allow for
covering the frame, and ½ inch from the length to allow for the seams,
and we have a bag 16 inches long by 14 inches deep.
And now to commence. Arrange the pieces of carpet on the board, and
mark off the size of each part required with a piece of chalk or
pipeclay. By cutting with the carpet, laying the right side up, we
shall be able to see that the pattern of it will be in the same
direction on both sides of the bag when made up. We next take the ball
of hemp, and by pushing the finger through the hole in the center of
it, drive out the end. To use the hemp from the inside is much the
best way, because the ball will stand perfectly still, whereas, if
started from the outside, it will be darting in all directions about
the floor of the workroom, and entwining itself around any obstacle
which lies there, unless it is placed securely in a box and drawn out
through a hole in the center of lid.
A hook must be fixed in some convenient place to make the waxends on,
or, as they are called in the trade, "threads," which term it will be
as well to call them by here; thus a _four-cord thread_ means a thread
or waxend containing four strands of hemp, a six-cord contains six
strands, and so on. One of the greatest difficulties for the amateur
is to produce a well-formed thread. He generally finds it thicker a
few inches from the point than at any other part. These are known in
the trade as bull-necked threads; and as the mechanic finds it
difficult to use them when his employer starts a new apprentice and
gives him this job for the men, I must impress on the worker here the
necessity of making them as perfect as possible. It would be as well
if a little practice was given at breaking the hemp in the way which
produces good points. Better waste a few yards of hemp than be
compelled to abandon a thread after making only a few stitches with
it.
Gripe the hemp firmly between the thumb and forefinger of the left
hand, leaving about eight or nine inches hanging loosely down; lay
this over the thigh of the right leg, and with the right hand rub it
in a downward direction, which will cause the twisted strand to
loosen. One good stroke should be sufficient; if not, it must be
repeated until the fibers forming the strand are quite loosened. By
holding it close to the end with the right hand, and giving it a jerk
with the left, the fibers will break, and the ends of the strands
formed in this way are placed at a little distance one above another,
which, when twisted, form a smooth, tapering point.
To cast off a thread the proper way is to stand at a distance of about
three feet from the hook previously mentioned, and by holding the end
of the hemp in the left hand, pass it over the hook and bring it down
with the right, then holding with the left and breaking as above. When
sufficient strands to form the thread have been broken off, carefully
examine the points to see that they taper properly, and have no lumps
in them. Rub the wax up and down a few times, so that the thread may
be properly waxed on that portion which will be inside when twisted.
Hold the two ends in the left hand, and with the right roll each end
separately down the right leg a sufficient number of times to twist
the thread throughout. Judgment will be required in this operation, or
the thread will be a constant source of trouble if it is over-twisted.
Wax it again, and then it is ready for use. See that the points are
well waxed, then take a needle and pass the point of the thread
through the eye until it nearly reaches that part which would stop its
progress.
It must now be turned down on to the thicker portion and carefully
twisted. Smooth it down, then take the other end of thread and another
needle, and fasten it on in the same way. In selecting the awl to be
used, do not take a very large one. The hole should be just large
enough for the thread to require a slight pull to get it through.
To commence sewing take one side and a gusset and place them evenly
together, the right side of the material being inside, and fix them in
the clams. Slip the welt as previously described between the edges,
and pass the awl through the lot. Drive it perfectly straight, as upon
this chiefly depends a nice seam when turned. Draw out the awl, and by
following the point, pass up the bottom needle with the left hand.
This should be taken by the thumb and forefinger of the right hand and
the thread pulled through half its length, so forming a thread of
equal length on each side. Make another hole with the awl about
one-third of an inch from the first. This gives the length of stitch.
Pass up the bottom needle as before into the right hand, the top
needle descending to the bottom immediately after. Take hold of this
with the left hand and pull through the threads simultaneously top and
bottom, until the extremity on each side lies on and forms the stitch.
Be careful that in pulling in the latter part each thread closes at
the same time, thereby preventing a crooked seam. Repeat until the
seam is finished, then take the other gusset and place in position.
Sew this, then take the other side of bag and sew to the gussets. You
will then have something in the shape of a bag, minus the bottom. Take
this next, and fix each corner to one of the seams previously made,
and stitch it carefully round, placing a welt in as before. At the end
of each seam a stitch or two back should be taken or the thread tied
over to prevent it opening.
The outside of the bag being inward, it must now be turned previous to
stiffening and framing. The turning is done by placing the bag over
the left arm, and with the right hand commence pushing in one of the
corners, then the opposite one until that end is reversed. Then serve
the other end in a similar manner, and smooth each seam along.
We now take a piece of stout millboard (an old ledger book cover will
do if large enough), or, if purchased with the frame, ask for a two
pound board: this will cost about 4d., and be sufficient for several
bags. Cut it quarter of an inch less than the bottom all round, and
see that it fits before gluing it in. To do this, place one end within
the seams at one end of the bag, and by lifting it in the middle press
in the other, when the stiffening will lie within the four seams at
the bottom. Having fitted it satisfactorily, take it out again and
glue it well with some good hot glue. This must be neither too thick
nor too thin. The best way to prepare it is to lay some glue in cold
water for twelve hours. It will absorb sufficient water in that time,
and can be boiled up without any further preparation. The quicker it
is fixed after the glue is put on the better. A brush similar to a
paint brush will be the best to apply it with, and need not cost more
than 6d. After the gluing, lay it aside for a few hours to allow it to
thoroughly set, during which time the making of the handles can be
proceeded with. On some bought bags these are very common, and seldom
last more than a few months; the usual plan being to take a piece of
rope about the size of a clothes line and roll a piece of brown paper
round it, covering it afterward with a piece of basil leather.
Procure two pieces of brown harness leather--the shoulder of the hide
is most suitable--from a saddler, 11 inches long by 1-1/8 inches wide,
round the four ends, and make a compass mark 1/8 of an inch from the
edge all round for the stitching. Take a piece of line as above, and
place within the leather, which most likely will have to be damped to
make it draw round easier. Leave 1½ inches from each end for sewing to
the bag, the line also being so much less than the full length of the
handles. Having sewn them, flatten the ends and bend the handles into
a semicircular shape, and leave them to dry.
By this time the glue holding the stiffening to the bottom of the bag
will be set, so the next move will be to put in the studs or nails.
Take the largest size awl and make five punctures through the bottom,
about three-quarters of an inch from each corner and one in the
center, as in Fig 8; push the nails through and turn down each of the
two claws in an opposite direction, tap them with a hammer to make
them lie closer, and also to prevent them from becoming loose. This
done, we next take the frame and remove the key-plate from it.
Fold the sides of the bag well over the frame, so that the stitching
will get a good hold of the part that goes inside. Put a stitch
through at each corner to hold it, and see that it sets perfectly true
on the frame. A space is left between the two plates of iron forming
the frame, which allows of the bag being sewn through it. Fix the
key-plate by riveting inside. Sew the bag from one corner of frame to
the other corner on each side, leaving the gussets unstitched. It is
now ready for the lining. Let this be good, as it will greatly add to
the durability of the bag if strong. Coarse linen at 8d. to 10d. per
yard is the best material for this purpose. The sides and bottom may
be cut in one piece; the length of this will be twice the depth of one
side of carpet (less the part which folds over the frame) and the
width of the bottom. The width of this piece throughout to be a half
inch less than the outsides were cut. The gusset lining will want to
be the same width as the gusset, but an inch less in length will do.
The seams of the lining may be stitched with an ordinary household
sewing machine if good thread is used. When made, place the lining
inside the bag, see that it is well down at the bottom, turn in the
top edge all round to the required size, and fix in as follows: Take a
long carpet needle and a length of thread, pass the needle through the
lining at the folded ridge and bring it up again through the same at a
distance of an inch or so. This forms a stitch within the lining; pass
the needle through one of the stitches made in sewing in the frame and
repeat as before, carefully observing that the lining falls into its
proper place as it is being sewn in. Continue in this way until the
two sides are done, leaving only the gussets and gusset lining to be
united. This is done by folding the edges inward and sewing them
together, the frame joints moving freely between the gussets and
lining. We have now only the handles to put on and it is complete. Sew
these on with a five cord thread well waxed. To protect the lock
against being unduly strained when filled, a strap and buckle may be
put on between the handles and each end of the frame, as in Fig. 3.
Next in order is the cricket bat bag, which should always be comprised
in the outfit of the amateur cricketer, as well as of the
professional. In making this we follow the instructions given for the
carpet bag. It may be made either of carpet, tan-canvas, or leather,
the latter, of course, being the strongest and most expensive. Carpet
will not require to be described, but a brief description of
tan-canvas and leather may be of service to the amateur in assisting
him to choose something for himself.
Tan-canvas, as used for bags and portmanteaux, is a strong, coarse
material of a brown color; it wears well, and has one advantage over
carpet--it is thoroughly waterproof.
Leather is, of course, superior to carpet or canvas, but there are a
few tricks in its manufacture which it may not be out of place here to
mention as a caution to the amateur that the old saying, "There's
nothing _like_ leather," is a thing of the past where the general
appearance of an article is meant. The genius of the inventor has
produced machinery which gives to paper, linen, and other stuffs the
appearance of the genuine article, whereas it does not contain one
particle of it. At one time, when a hide of leather was required to be
of the same thickness all over it, the currier would work at the flesh
of the skin with a shaving knife, gradually scraping the thick parts
away until it was reduced to the required substance. Now it is done
in a few minutes. The hide is passed whole between the rollers of a
splitting machine against the sharp edge of a knife, which reaches
from one side of the machine to the other, a distance of 10 or 12
feet. This knife is so gauged that any thickness can be taken off at
one operation, the part taken off resembling the hide in size and
shape. The top or grain of the hide is then dressed and finished off
brown, if for brown hides; or, if to be used for enameled hides, they
are dyed and japanned. These are called either brown or enameled
cow-hides, according as they are finished off, and are used for all
the best class of Gladstone, brief, and other bags. The bottom or
fleshing of the hide is also dyed and japanned, and when finished,
exactly resembles in appearance the hide itself, and is very difficult
for the novice to tell when made up into bags or any other article.
These are called _splits_, and having had the best part of the skin
taken from them, do not wear one-fourth the time the grain will. The
black enamel soon chips off, which gives them a worn-out appearance.
To make a bag 36 inches by 12 inches by 8 inches requires a frame 36
inches long, the sides 36½ inches by 14 inches, gussets 14 inches by
8½ inches, bottom 36½ inches by 8 inches. The lining will be 36 inches
by 12 inches for the sides, gussets 13 inches by 8 inches, bottom 36
inches by 8 inches. For the handles two pieces of leather 12 inches by
2 inches. The straps and chapes are sewn on quite close to the frame,
straps 10 inches long by 1 inch, chapes 4½ inches by 1 inch. Cut a
slit in the middle of the chape for the buckle tongue to go through,
and pare the under side at the end so that it is not too lumpy when
sewn on to the bag. Cut two loops 3 inches long by ¾ inch wide for the
points of straps to go through.
The brief bag must be made of leather, and as there is the same amount
of work in making it, whether it be of split or hide, it will be sure
to give greater satisfaction if the latter is chosen. The manufacture
of this bag differs considerably from the others. The sides and
gussets in the carpet bag are cut straight from top to bottom, but in
the brief bag they must be shaped to fit the frame, and give it a more
comely appearance. The frame, as before described, is quite different.
The way to commence with this bag is to open the frame as in Fig. 7,
so that it will lie perfectly flat upon the bench. With the rule
measure it carefully between the corners, A, A, and again at A, B. The
distance between A and B being less when the frame is open than when
closed, an additional ½ inch must be added to allow the gusset to bend
freely round the hinge. Having correctly taken these measurements, get
a sheet of brown paper and fold it in the middle; the reason for this
is to allow of each side of the pattern taking the same curve at the
swelled part. Cut the pattern for the sides first by ascertaining half
the distance, A, A, and marking it on to the edge of the paper,
measuring from the folded edge toward the ends. Next mark on the
folded edge the depth you intend the bag to be, allowing in this, as
in the carpet bag, 1½ inches for covering the frame. The depths of
brief bags vary so much that I will give these only as a guide,
leaving my readers to add or reduce as their fancy guides them; but if
they should strictly adhere to these given below, I am certain they
will find them very useful sizes.
For a 12 inch frame cut the sides and gussets 10½ inches in depth;
when made up, these will be 9 inches from the frame to the bottom. For
a 14 inch frame add 1 inch, and for a 16 inch add 2 inches. This will
make these 10 inches and 11 inches in depth respectively when made up,
and either of these will be found a very useful bag for many purposes.
The width of the bottoms to be cut 5 inches, 5½ inches, and 6 inches,
the 5 inch, of course, for the 12 inch bag, the 5½ inch for the 14
inch, and the 6 inch for the 16 inch. The depth having been decided
upon, and marked on the folded edge of the paper, make another mark
the same distance from the edge at the first mark, H. The bottom of
the sides being 1 inch longer than the top, add ½ inch to the
measurement of the top of pattern when the bottom part is marked off
at J L. Draw a curved line between H L, as in Fig. 9, and cut through
the two thicknesses of paper at one time, keeping them well together
to insure them being alike. The gusset pattern may be cut in the same
way, D to D, Fig. 10, being half the distance of A B, Fig. 7, and the
½ inch added for going round the joint; E E, the swelled part, which
bends into the bag when the frame is closed, and also allows it to
open perfectly square; F F is half the width of the bottom of gusset.
A pattern for the bottom of the bag may be made by folding a piece of
paper each way to get the length and width; make a small hole through
the four thicknesses, open it and mark it from hole to hole, using the
rule as a guide. This will be found to be perfectly accurate.
To cut out the bag, lay the leather on the bench, enameled side
downward, and see that the patterns lie on it so the creases will run
from the top to bottom of the bag when made. The sides must be taken
first, and as they are more exposed than any other part, they should
be taken from the best part of the hide. Take the gussets next, then
the bottom. The welts are taken from the cuttings which are left. To
make the handle, glue a lot of odd pieces together about 6½ inches
long, ½ inch wide, and the same thickness, and when dry pare the edges
away until it is perfectly round and slightly tapering toward each
end. It is then divided and glued top and bottom to a strip of good
leather cut to shape, Fig. 12, which is passed through the rings at
each end, and turned back to form a shape. Put a few stitches through
close to the rings before the fittings are glued on, and cover with a
piece of cow-hide long enough to go through the two rings and along
the under side, then stitch it. Trim and dye the edges, rubbing them
afterward with a piece of cloth to produce a polish. Before making the
handle, the plates must be on the rings, or it will prove a difficult
job to get them on afterward.
The stiffening for the bottom will be cut as if for a carpet bag. Fig.
11 represents the stiffening for the gussets, and is cut from a board
half the thickness of that used for the bottom.
The linings may be cut from the outside patterns by reducing them the
1½ inches, allowed for covering the frame, and 1/8 inch for each welt.
A lining of scarlet or blue roan greatly adds to the appearance and
durability of a bag. A skin large enough for a 14 inch or 16 inch will
cost about 3s.
Cow-hide for the outside is sold at 1s. 8d. per square foot, but the
leather sellers frequently have pieces large enough for making a bag
which they will sell at a slight reduction, and which answers this
purpose as well as cutting a hide. In seaming the bag, take care not
to wrinkle it in the clams. The welts in this must reach only to the
frame, the same as in the carpet bag; the rest of the seam must be
neatly closed and rubbed down, so that it will not be lumpy on the
frame. Before turning the bag warm it before the fire, especially if
it is cold weather. Glue in the bottom stiffening first, and then the
gussets, rubbing them well down with the bone. When these are set,
prepare for the operation of framing. Fold one of the sides to get the
middle of it, cut a hole for the lock barrel about 1¼ inches from the
edge, and press it over. Be careful not to cut it too large or the
hole will show. Pierce a hole through the leather for the lock plate,
press this tightly on the frame, and clinch the clams underneath, to
hold it securely. Make holes for the handle plates and fasten them on
in a similar manner. Two slits must be cut near the middle of the
other side of bag, about ¾ inch from the edge, for the hasp to go
through. This bag must be sewn to the frame all round, and care must
be taken that a sufficient fullness is allowed in the middle of the
gusset to enable it to close easily round the joints of the frame. A
thumbpiece must be sewn on the bag at the hasp to open it by. The
lining of this bag is sewn through the frame all round in the same
manner as the side linings of the carpet bag.
I hope my readers will not think that I have gone too much into
details. It is in small things that so many failures take place. As it
is much easier to do anything when you are shown than when so much has
to be guessed, it is my desire to make the road for beginners as
smooth as possible, which must be my excuse if any is required. It is
as well that those who intend to turn their attention to working in
leather should begin by making a bag; the experience gained in
cutting, fitting, putting together, and finishing will be useful when
larger and more difficult pieces of work are undertaken.--_Amateur
Mechanics._
* * * * *
MOLASSES, HOW MADE.
The _New England Grocer_ says that the manufacture of molasses is
really the manufacture of sugar up to a certain stage, for molasses is
the uncrystallized sirup produced in the making of sugar. The methods
of manufacture in the West Indies vary very considerably. In the
interior and on the smaller plantations it is made by a very primitive
process, while on the larger plantations all the appliances of modern
science and ingenuity are brought to bear. Each planter makes his own
sugar. It is then carried to the sea coast and sold to the exporters,
by whom it is shipped to this country. The quality and grade of the
molasses varies with each plantation. Two plantations side by side may
produce entirely different grades. This is owing to the soil, which in
Porto Rico and other localities in the West Indies seems to change
with almost every acre. The cane from which the sugar and molasses is
made is planted by laying several pieces of it in holes or trenches.
The pieces are then covered with earth to the depth of two or three
inches. In about two weeks sprouts appear above the surface. Then more
earth is put in, and as the sprouts grow, earth is added until in
three or four months the holes are filled up. The planting is done
from August to November, and the cutting progresses throughout the
greater part of the year. The cane grows to a height of seven or eight
feet, in joints each about a foot long.
When the cane is in proper condition for cutting, as shown by its
appearance, an army of workmen take possession of the field. Each is
armed with a long, broad knife, like a butcher's cleaver. They move
down the lines of cane like an army, and while the cutting is going on
the fields present an interesting sight, the sword-like knives
flashing in the sun, the 300 or 400 laborers, the carpet of cut cane,
the long line of moving carts, and the sea of standing cane, sometimes
extending for miles and miles, stirred by the breeze into waves of
undulating green. The laborers employed on these plantations are
largely negroes and Chinese coolies. When the cane is ripe, they
proceed to the field, each armed with a _matchet_. Spreading over the
plantation, they commence the cutting of the cane, first by one cut at
the top, which takes off the long leaves and that part which is
worthless, except as fodder for the cattle. A second cut is then given
as near the root as possible, as the nearer the ground the richer the
cane is in juice. The cut cane is allowed to fall carelessly to the
ground.
Other workmen come with carts, pick it up, tie it in bundles and
carry it to the mill. The cutting of the cane is so adjusted as to
keep pace with the action of the mill, so that both are always at
work. Two gangs of men are frequently employed, and work goes on far
into the night during the season, which lasts the greater part of the
year.
As before stated, some of the methods of manufacture are very simple.
In the simplest form, the sugar cane is crushed in a mortar. The juice
thus extracted is boiled in common open pans. After boiling a certain
length of time, it becomes a dark colored, soft, viscid mass. The
uncrystallized sirup is expressed by putting the whole into cloth bags
and subjecting them to pressure. This is molasses in a crude state. It
is further purified by reboiling it with an addition of an alkaline
solution and a quantity of milk. When this has continued until scum no
longer arises, it is evaporated and then transferred to earthen jars.
After it has been left for a few days to granulate, holes in the
bottom of the jars are unstopped, and the molasses drains off into
vessels placed to receive it. Another process of extracting molasses
is as follows: By various processes of boiling and straining, the
juice is brought to a state where it is a soft mass of crystals,
embedded in a thick, but uncrystallized, fluid. The separation of this
fluid is the next process, and is perfected in the curing house, so
called. This is a large building, with a cellar which forms the
molasses reservoir. Over this reservoir is an open framework of
joists, upon which stands a number of empty potting casks. Each of
these has eight or ten holes bored through the bottom, and in each
hole is placed the stalk of a plantain leaf. The soft, concrete mass
of sugar is removed from the cooling pans in which it has been brought
from the boilers and placed in the casks. The molasses then gradually
drains from the crystallized portion into the reservoir below,
percolating through the spongy plantain stalks.
On the larger plantations, machinery of very elaborate description is
used, and the most advanced processes known to science are employed in
the manufacture. The principle is, however, the same as has been seen
in the account of the simpler processes. On these larger plantations
there are extensive buildings, quarters for workmen, steam engines,
and all the necessary adjuncts of advanced manufacturing science. In
the sugar mills the cut cane is carried in carts to the mill. It is
then thrown by hand upon an endless flexible conductor which carries
the cane between heavy crushers. The great jaws of the crushers press
the cane into pulp, when it is thrown aside automatically to be carted
away and used as a fertilizer. The juice runs off in the channels of
the conductor into huge pans. The juice is now of a dull gray color
and of a sweet, pleasant taste, and is known as _guarapo_. It must be
clarified at once, for it is of so fermentable a nature that in the
climate of Porto Rico it will run into fermentation inside of half an
hour if the process of clarifying is not commenced. The pans into
which the juice is conducted are pierced like a colander. The liquor
runs through, leaving the refuse matter behind. It is then forced into
tanks by a pump and run to the clarifiers, which are large kettles
heated by steam. Lime is used to assist the clarification. It is then
filtered into vats filled with bone black. The filtering is repeated
until the juice changes color, when it is conveyed to the vacuum pans.
It has now become a thick sirup. It is then pumped into the sirup
clarifiers, skimmed, and again run through bone black, and finally is
conducted into another kettle, where it is allowed to crystallize. The
sirup that fails to crystallize is molasses, and it is here that we
catch up with what we started after. To extract the molasses from the
crystallized mass of sugar, we must go to the purging house. This is
similar to the building spoken of in connection with the simpler
process. It is of two stories. The upper floor is merely a series of
strong frames with apertures for funnel-shaped cylinders. The sugar is
brought into the purging house in great pans, which are placed over
the funnels. The pans are pierced with holes through which the
molasses drains off into troughs which are underneath the floor, all
running to a main trough. From thence the molasses runs into vats,
called _bocoyes_, each of which holds from 1,200 to 1,500 gallons. The
hogsheads in which the molasses is brought to this country are
manufactured principally in Philadelphia and taken to the West Indies.
They are placed in the hold of the vessel and the molasses pumped into
them. The government standard for molasses is 56 degrees polarization.
When not above that test, the duty is four cents per gallon. Above it
the duty is eight cents. This tends to keep molasses pure, as the
addition of glucose increases the quantity of sugar and therefore of
the polarization, and would make necessary the payment of increased
duties. The adulteration of molasses is therefore largely if not
wholly done after it is out of bond and in the hands of the jobber.
* * * * *
PRIMITIVE IRON MANUFACTURE.
We are indebted for the illustrations and the particulars to Dr.
Percy's invaluable book on iron and steel (probably it is not saying
too much to describe it as the best work on the subject ever written).
[Illustration: SECTION OF INDIAN BLAST FURNACE AND BLOWING MACHINE.]
Fig. 1 shows a sectional elevation, and Fig. 2 shows a plan of furnace
and bellows and tuyeres, indeed, an entire ironworks plant used in
India, not only now, but, so far as we can gather, from time
immemorial. The two figures give a sufficiently clear idea of the form
of furnace used in Lower Bengal, in which portion of our Indian empire
there are entire villages exclusively inhabited by iron smelters, who,
sad to relate, are distinguished from the agricultural villages
surrounding them by their filth, poverty, and generally degraded
condition. There are whole tribes in India who have no other
occupation than iron smelting. They, of course, sink no shafts and
open no mines, and are not permanent in any place. They simply remain
in one place so long as plentiful supplies of ore and wood are
obtainable in the immediate vicinity. In many cases the villages
formerly inhabited by them have passed out of existence, but the
waste, or rather wasted products, of their operations remain.
The furnace shown in Figs. 1 and 2 is built of the sandy soil of the
district, moistened and kneaded and generally strengthened by a sort
of skeleton of strips of flexible wood. In form it varies from a
cylinder, more or less circular, diverging into a tolerably acute
cone, the walls being about 3 in. thick. The height is generally
about 3 ft. and the mean internal diameter about 1 ft., but all these
dimensions vary with different workmen and in different localities.
There are two apertures at the base of the furnace; one in front,
about 1 ft. in height, and rather less in width than the internal
diameter of the furnace, through which, when the smelting of one
charge is finished, the resulting mass of spongy iron is extracted,
and which during the smelting is well plastered up, the small conical
tuyere being inserted at the bottom. This tuyere is usually made of
the same material as the furnace--namely, of a sandy soil; worked by
hand into the required form and sun-dried; but sometimes no other
tuyere is employed than a lump of moist clay with a hole in it, into
which the bamboo pipes communicating with the bellows are inserted.
The other aperture is smaller, and placed at one side of the furnace,
and chiefly below the ground, forming a communication between the
bottom of the furnace chamber and a small trench into which the slag
flows and filters out through a small pile of charcoal. It is this
slag being found in places where iron is not now made that shows that
iron smelting was an occupation there, perhaps many centuries before.
The inclined tray shown at the top of the furnace on Fig. 1 is made of
the same material as the furnace itself, and when kneaded into shape
is supported on a wooden framework. On it is piled a supply of
charcoal, which is raked into the furnace when required.
The blowing apparatus is singularly ingenious, and is certainly as
economical of manual labor as a blowing arrangement depending on
manual labor well can be. A section of the bellows forms the portion
to the right of Fig. 1, showing tuyere forming the connection between
bellows and furnace. It consists of a circular segment of hard wood,
rudely hollowed, and having a piece of buffalo hide with a small hole
in its center tied over the top. Into this hole a strong cord is
passed, with a small piece of wood attached to the end to keep it
inside the bellows, while the other end is attached to a bent bamboo
firmly fixed into the ground close by. This bamboo acts as a spring,
drawing up the string, and consequently the leather cover of the
bellows, to its utmost stretch, while air enters through the central
hole. When thus filled, a man places his foot on the hide, closing the
central hole with his heel, and then throwing the whole weight of his
body on to that foot, he depresses the hide, and drives the air out
through a bamboo tube inserted in the side and communicating with the
furnace. At the same time he pulls down the bamboo with the arm of
that side. Two such bellows are placed side by side, a thin bamboo
tube attached to each, and both entering the one tuyere; and so by
jumping on each bellows alternately, the workman keeps up a continuous
blast.
[Illustration: Fig. 2.--PLAN OF INDIAN BLAST FURNACE AND BLOWING
MACHINE.]
The Figs. 1 and 2 are taken from sketches, and the description from
particulars, by Mr. Blandford, who was for some years on the
Geological Survey of India, and had exceptional opportunities in his
journeyings of observing the customs and occupations of the Indian
iron smelters. The blowing machine is an especially wonderful and
effective machine, and was first described and illustrated by Mr.
Robert Rose, in a Calcutta publication, more than half a century ago.
He also had seen it used in iron making in India.--_Colliery
Guardian._
* * * * *
WOOD OIL.
Wood oil is now made on a large scale in Sweden from the refuse of
timber cuttings and forest clearings, and from stumps and roots.
Although it cannot well be burned in common lamps, on account of the
heavy proportion of carbon it contains, it is said to furnish a
satisfactory light in lamps specially made for it; and in its natural
state it is the cheapest illuminating oil. There are some thirty
factories engaged in its production, and they turn out about 40,000
liters of the oil daily. Turpentine, creosote, acetic acid, charcoal,
coal-tar oils, etc., are also obtained from the same materials as the
wood oil.
* * * * *
SOAP.
By HENRY LEFFMANN, M.D.
Although the use of soap dates from a rather remote period, the
chemist is still living, at an advanced age, to whom we are indebted
for a knowledge of its composition and mode of formation. Considerably
more than a generation has elapsed since Chevreul announced these
facts, but a full appreciation of the principles involved is scarcely
realized outside of the circle of professional chemists. Learned
medical and physiological writers often speak of glycerin as the
"sweet principle of fats," or term fats compounds of fatty acids and
glycerin. Indeed, there is little doubt that the great popularity of
glycerin as an emollient arose from the view that it represented the
essential base of the fats. With regard to soap, also, much erroneous
and indistinct impression prevails. Its detergent action is sometimes
supposed to be due to the free alkali, whereas a well-made soap is
practically neutral.
A desire to secure either an increased detergent, cleansing, or other
local effect has led in recent years to the introduction into soaps of
a large number of substances, some of which have been chosen without
much regard to their chemical relations to the soap itself. The result
has been the enrichment of the materia medica with a collection of
articles of which some are useful, and others worse than useless. The
extension of the list of disinfectant and antiseptic agents and the
increased importance of the agents, in surgery, have naturally
suggested the plan of incorporating them with soaps, in which form
they will be most convenient for application. Accordingly, the
circulars of the manufacturing pharmacists have prominently displayed
the advantages of various disinfecting soaps.
Among these is a so-called corrosive sublimate soap, of which several
brands are on sale. One of these, containing one per cent. of
corrosive sublimate, is put on the market in cakes weighing about
sixteen hundred grains, and each cake, therefore, contains sixteen
grains of the drug--a rather large quantity, perhaps, when it is
remembered that four grains is a fatal dose. Fortunately, however, for
the prevention of accidents, but unfortunately for the therapeutic
value of the soap, a decomposition of the sublimate occurs as soon as
it is incorporated in the soap mass, by which an insoluble mercurial
soap is formed. This change takes place independently of the alkali
used in the soap; in fact, as mentioned above, a well-made soap
contains no appreciable amount of free alkali, but is due to the
action of the fat acids. Corrosive sublimate is _incompatible_ with
any ordinary soap mass, and this incompatibility includes not only
other soluble mercurial salts, but also almost all the mineral
antiseptics, such as zinc chloride, copper sulphate, iron salts. Some
of the preparations of arsenic may, however, be incorporated with soap
without decomposition.
Such being the chemical facts, we must admit that no reliance can be
placed in corrosive sublimate soaps as germicide agents. It must not
be supposed that this incompatibility interferes with the use of these
soaps for general therapeutic purposes. It is only the specific
germicide value which is destroyed. Since the fats used in soap
manufacture yield oleic acid, we will have a certain amount of
mercuric oleates formed together with stearate and other salts, and
for
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