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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.]