Chapter 1

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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.

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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..."

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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.

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.

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.

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.

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._

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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.