Popular Science Monthly/Volume 56/February 1900/The Applications of Explosives II

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THE APPLICATIONS OF EXPLOSIVES.
By CHARLES E. MUNROE,

PROFESSOR OF CHEMISTRY, COLUMBIAN UNIVERSITY.

[Concluded.]

IT is apparent that the range of even the most highly perfected torpedo is comparatively short, while their accuracy of travel is low. Besides, their propelling, controlling, and discharging mechanisms are complicated, delicate, and easily deranged, they are very expensive, and not only the explosive chamber but the entire system is destroyed in use. The superiority of gunpowder guns as a means of throwing projectiles to great distances with accuracy is well known, and their capacity for safely and efficiently projecting shells filled with gunpowder has long been demonstrated. It was obvious that as the superior destructive power of dynamite, gun cotton, and other high explosives became known and their commercial manufacture was assured, attempts would be made to employ them as PSM V56 D0458 Gun cotton shell after impact.pngGun-Cotton Shell after Impact. bursting charges for shells. Experiments to demonstrate how this might be done and what effects could be expected were begun more than forty years ago, and have been continued in many different places from time to time ever since; but while it has proved that small charges might be fired with low velocities and pressures in ordinary shell, and large charges in specially constructed shell or in specially prepared forms of charge, with comparative safety so far as the premature explosion of the explosive charge itself is concerned, yet these bodies are so sensitive to the shock resulting from the discharge of the propellant, the heat generated by its combustion, and that arising from friction in the "set-back" of the shell charge and the rotation imparted by the rifling, that they can not be safely fired from modern high-power guns under service conditions, particularly as these explosives all require that the shell shall be fitted with a detonator in order that the charge may be fully exploded. The most promising results with explosives of this class have been obtained with compressed wet gun cotton, which has been packed directly in the shell in rigid blocks completely filling the shell cavity, or cut in cubes and cemented in the cavity with carnauba wax, for shell filled in the former manner, but unfused, were repeatedly fired, in 1887 and 1888, at Newport, R. I., from 24-pounder Dahlgren howitzers and

PSM V56 D0459 Sims dudley pneumatic gun limbered up.png
Sims-Dudley Pneumatic Gun, limbered up.
(Courtesy of the Scientific American.)

20-pounder muzzle-loading rifles with service charges of powder, and though they were fired point blank into the masonry escarpment of the old fort on Rose Island, but fifty yards distant from the muzzle, so that the shells were broken up or distorted and the gun cotton in them subjected to a powerful compression, yet not only was there no premature explosion, but none of the shell

PSM V56 D0459 Sims dudley pneumatic gun in battery.png
Sims-Dudley Pneumatic Gun, in Battery.
(Courtesy of the Scientific American.)

exploded by impact. About the same time fused shell containing cemented gun cotton were fired in Germany, with an initial velocity of fourteen hundred feet per second, and they passed completely through four inches and three quarters of compound armor, backed with twenty-four inches of oak, and burst inside the bombproof, while in 1897 fused armor-piercing shells containing wet gun cotton were fired from the six-inch quick-firing gun, with a muzzle velocity of nearly nineteen hundred PSM V56 D0460 Tyndall bell mouthed bronze gun.pngTyndall's Bronze Bell-Mouthed Gun. feet per second, which completely perforated three inches of steel and burst behind the plate. Encouraged by these results, this system was adopted by our army officials, but, on trial in larger calibers at Sandy Hook, it gave rise to premature explosions, and the tale of disaster reached its climax on April 29, 1899, when Captain Stuart, of the Ordnance Corps, was superintending the loading of a twelve-inch torpedo shell with wet gun cotton by compressing it into the shell, for an explosion resulted which killed four men instantly and fatally wounded two others. Captain Stuart being one of them.

The history of the attempts made to use nitroglycerin, dynamite, explosive gelatin, and explosives of this class as bursting charges for shell fired from service guns is even less satisfactory than that given for gun cotton. It is not surprising, therefore, that inventors should have proposed catapults, slings, rotary wheels, and other means for projecting these powerful agents into the enemy's midst, but the Mefford air gun, as mounted on the United States steamship Vesuvius, and the Sims-Dudley gun, in which a reduced charge of powder is fired in a chamber PSM V56 D0460 Reflector in which gun cotton is fired.pngMirror or Reflector in which to fire Gun Cotton. exterior to the gun proper, were deemed to possess sufficient merit to warrant their trial in the field. These devices were employed in the recent war with Spain, the pneumatic guns on the Vesuvius being used to throw shells containing three hundred pounds of gin cotton, while the Sims-Dudley guns were used on land to throw small charges of dynamite or explosive gelatin; but, beyond frightening the enemy by the startling character of their reports, these superficial charges produced no serious effect. There is a widespread misapprehension in regard to the devastating effect of these high explosives, for when unconfined the effect even of large charges of them upon structures is comparatively slight. At the Naval Ordnance Proving Ground, so long ago as 1884, repeated charges of dynamite, varying from five pounds to one hundred pounds in weight, PSM V56 D0461 Railroad torpedoes fastened to rail.pngRailroad Torpedoes fastened on Rail. were detonated on the face of a vertical target consisting of eleven one-inch wrought-iron plates bolted to a twenty-inch oak backing, until 440 pounds of dynamite had been so detonated in contact with it, and yet the target remained practically uninjured; while at Braamfontein the accidental explosion of fifty-five tons of blasting gelatin, which was stored in railway vans, excavated but 30,000 tons of soft earth. This last may seem a terrible effect, but the amount of explosive involved was enormous and the material one of the most energetic that we possess, while if we compare it with the action of explosives when confined its effect becomes quite moderate. Thus at Fort Lee, on the Hudson, but two tons of dynamite placed in a chamber in the rock and tamped brought down 100,000 tons of the rock; at Lamberis, Wales, two tons and a half of gelatin dynamite similarly placed threw out 180,000 tons of rock; and at the Talcen Mawr, in Wales, seven tons of gunpowder, placed in two chambers in the rock, dislodged from 125,000 to 200,000 tons of rock. We might cite many such examples, but on comparing these we find that the gunpowder confined in the interior at the Talcen Mawr was over forty-two times as efficient as the explosive gelatin on the surface at Braamfontein, PSM V56 D0461 Steel test disks for measuring gun cotton explosion.pngSteel Disks upon which Gun Cotton has been detonated to test their Resistance to Shock. Midvale steel disks after second fire. while the dynamite at Fort Lee was over ninety times as destructive.

Considerations similar to these led me, in 1885,[1] to point out that high explosives for use in shells must be strongly confined, and in the attack on armored ships they should be fired in projectiles that can "either penetrate the armor partially and explode in place or pierce it completely and burst inside the ship" to secure the greatest efficiency. This requires that the projectiles shall be fired at higher velocities than can be imparted to them by guns of the kind just described, and which can only be realized at present in modern breech-loading rifles. Although experience has shown the futility of all our efforts to use gun cotton and nitroglycerin explosives in this manner, it has been proved that the nitro-substitution explosives can be employed with safety and effect.

The nitro-substitution explosives are made from nitrobenzenes, nitrotoluenes, nitronaphthalenes, nitrophenols, and bodies of a similar character, and one of them, called joveite, has given excellent results in this country. After having demonstrated that the destructive effect of joveite was greater than that of gunpowder, smokeless powder, or gun cotton, PSM V56 D0462 Shooting an oil well with nitroglycerin.pngShooting an Oil Well with Nitroglycerin. and, by repeated trials under severe conditions, that service shell loaded with it could be fired from service guns under service conditions with safety, on November 3, 1897, the naval officials at Indian Head fired a fused ten-inch Carpenter armor-piercing projectile containing 8.25 pounds of joveite, with a velocity of 1,960 foot-seconds, at a Harveyized nickel-steel plate taken from the armor for the United States steamship Kentucky. The shell passed completely through the armor plate, where it was 14.5 inches in thickness, and burst immediately behind the plate, [n a second round an unfused ten-inch Midvale semi-armor piercing shell containing twenty-eight pounds of joveite was fired with a velocity of 1,925 foot-seconds at the same plate where it was sixteen inches thick. The shell penetrated to a depth of twelve inches, and the heat produced by the upsetting of the shell was so great as to explode the joveite, which broke the plate and burst the shell with tremendous violence. In fact, the explosion was so very severe that the heavy base plug of the shell was sheared longitudinally, an effect never observed] before with any explosive fired at the proving ground.

Notwithstanding that no accident occurred in any of the many firings, that the stability and safety of the explosive are assured, and that the explosion has been effected with a well-known and PSM V56 D0463 Safe to be opened by detonation with nitroglycerin.pngSafe to be opened by Detonation of Nitroglycerin. Before the charge was fired. long-used form of fuse, no provision has yet been made to supply the service with charges for its costly armor-piercing projectiles.

Happily, the force resident in explosives may be applied to the saving as well as to the destruction of human life, advantage having long since been taken of the penetrating power of the report from the discharge of a gun to employ them as signals of distress at sea or as warnings in foggy weather. The English Lighthouse Board, under Professor Tyndall's guidance, some years ago sought to find the form of gun best suited to this purpose, and their experiments led them at first to a bronze gun with a bell-shaped mouth. Subsequently, their attention being called to the sharpness and carrying power of the report from detonating gun cotton, an apparatus was devised in which the gun cotton was detonated in the focus of a parabolic mirror. The best results, however, PSM V56 D0463 Safe blown apart after firing charge.pngAfter firing Charge. were attained with rockets carrying gun-cotton charges arranged to be exploded in mid air.

Guns have also been arranged for projecting life-lines between stranded ships and the adjacent shore, and are now employed on a smaller scale for conveying lines to the upper stories of our monumental buildings when they are on fire.

By means of guns or rockets, projectiles filled with oil may be cast to considerable distances from a vessel in a raging sea, so that the oil, as it diffuses, may still the waters in her course; while sounding-lines may be thrown far in advance of a vessel while she is still under way, and the soundings taken without her laying-to.

Inclosed in shallow tin boxes, which are fixed by lead strips to the top of the rail, explosives are used as torpedoes in the railroad service to give warning, by the report of their explosion as an engine runs over them, that another train is on the same track and but a short distance ahead, and by this means collisions in fogs or on curves are frequently prevented.

Explosives find applications in many industries. The farmer uses them in breaking bowlders, grubbing stumps and felling trees, in shaking the soil to fit it for deep-soil cultivation, and, in the wine-growing districts, to free it from phylloxera, PSM V56 D0464 Safe perforated by hollow dynamite cartridge.pngSafe perforated by Hollow Dynamite Cartridge. while the farmer's friend has tried by this means, in times of drought, to shake the nerves of Jove and to divert the hailstorm from its course.

The iron founder uses them in breaking up large castings. The iron smelter employs them to clear out obstructions in blast furnaces while the latter are still in operation, the dynamite, protected by a clay envelope, being inserted in the red hot mass which clogs the furnace. The author has proposed to use the detonating explosives for testing the integrity of large masses of metals and their resistance to shock.

Dynamite has been employed in fishing, since submarine explosions of it will kill or stun fish for a long distance about the charge. This method of fishing, which threatened to deplete the waters, has very properly been prohibited by law, but guns are employed for projecting harpoons in the whale fishery, and have reduced very much the danger attending this extra-hazardous occupation.

Nitroglycerin, inclosed in tin cans three to five inches in diameter and five to twenty-five feet in length, is used for shooting oil wells to free them from the solid paraffins with which they become choked, or to shake the oil-bearing sandstone so as to produce a greater yield. In this work the loaded can, having a detonating cap attached to its top, is lowered by a wire to the bottom of the well. which is often fifteen hundred feet or more in depth. A perforated weight is then strung on the wire, and when the torpedo is in place the weight is allowed to fall, strike the cap, PSM V56 D0465 Hollow dynamite cartridge elevation view.pngHollow Dynamite Cartridge; Elevation. and explode the charge.

Dynamite has been used to knock out the blocking from the ways when launching ships. Fired on an iron plate placed on the top of a pile and covered with a tamping of earth or clay, it has successfully and economically replaced the pile driver. It has been found efficient in excavating holes in which to plant telegraph and telephone poles; in driving water out of quicksands in which foundations are to be laid or shafts to be driven; in slaughtering cattle; in breaking down ice dams to prevent inundations; in blowing up buildings to prevent the spread of conflagrations; in razing unsafe walls of burned buildings; in destroying wrecks which endanger navigation, and even in freeing vessels which arc hard aground on shoals.

An especially notable instance was in the blasting out of the débris in the river at Johnstown after the frightful flood that occurred there, which formed an enormous dam above the bridge and threatened its existence, PSM V56 D0465 Hollow dynamite cartridge view from below.pngHollow Dynamite Cartridge.
View from below.
and which was successfully and expeditiously removed by blasting after all other means had been tried in vain.

In fact, the amount of explosives consumed in the industries is so great that the quantity employed for military purposes sinks into insignificance. Yet we have failed to refer to those industries—quarrying and mining, and the engineering operations—in which they are most extensively and commonly used, being employed so largely in mining alone that it is an almost daily occurrence for blasts containing twenty, thirty, and even fifty thousand pounds of explosives to be used in a single charge; and the system of large blasts has even become common in hard-rock excavations, such as quarries and railroad cuttings, while in the blast at the blowing up of Flood Rock, in New York Harbor, October 10, 1885, over one hundred and forty-one PSM V56 D0466 Testing the efficiency of gun cotton.pngFiring on Iron Disk, testing on Lead Disk, in testing the Efficiency of Gun Cotton. tons of rack-a-rock, dynamite, and mercury fulminate were used in a single shot.

Nor have I alluded to the use of explosives by the anarchists in their dastardly outrages, through which the safety of the old and young, feeble and strong, the innocent and the offending, are alike endangered; but I will touch briefly upon the implications of these powerful agents in the too-much cultivated industry of safe-robbing, since I was called upon some years ago to demonstrate, before a Government commission, how safes might be successfully attacked either in a burglarious way or by a mob with explosives, meaning by the burglarious operation that the safe should be made accessible within twenty-four hours with means such as a party of men could smuggle into a bank and which might be used without attracting attention or doing material damage to the building, and by "mob violence," meaning that the vaults are supposed to be in the hands of a mob which has ample time and quantities of explosives at command, and does not care how much noise is made or destruction is wrought, provided the treasure is secured.

In the experiments made in a burglarious way, among others, a three-thousand-dollar square safe of the most approved construction was attacked by inserting in the crevice about the locked door four and eight tenths ounces of nitroglycerin, and in eight minutes PSM V56 D0466 Gun cotton disk.pngGun-Cotton Disk. With indented inscription, and iron plate upon which the indented inscription has been reproduced. after the operation of loading was begun the charge was fired, with the result that the whole of the jamb below the door was blown out and a hole made in the door of sufficient size to admit the hand and arm, while the doors and divisions of the interior compartments were completely shattered. On repeating the operation with four ounces and a quarter of forcite dynamite the door was completely torn off. Among experiments made to demonstrate the resistance of structures to attack by a mob was one upon a safe twenty-nine inches cube, with walls four inches and three quarters thick, made up of plates of iron and steel, which were re-enforced on each edge so as to make it highly resisting, yet when a hollow charge of dynamite nine pounds and a half in weight and untamped was detonated on it a hole three inches in diameter was blown clear through the wall, though a solid cartridge of the same weight and of the same material produced no material effect. The hollow cartridge was made by tying the sticks of dynamite around a tin can, the open mouth of the latter being placed downward, and I was led to construct such hollow cartridge for use where a penetrating effect is desired by the following observations:

In molding the gun cotton at the torpedo station, as stated above, a vertical hole was formed in each cylinder or block in which to insert the detonator, PSM V56 D0467 Holes produced in iron plates by bored gun cotton.pngHoles produced in Iron Plates by bored Gun Cotton. and in the final press a steel die was laid upon the cake so that an inscription in letters and figures was forced upon it. This inscription was indented in the cylinders and was raised upon the surfaces of the blocks. When the gun cotton was fired untamped, in testing it, the cylinder or block was usually placed with the inscribed face resting on a polished iron plate or iron disk, and after firing, if the gun cotton had detonated it was invariably found that not only was a vortexlike cavity produced below the detonator, but that the inscription on the gun cotton was reproduced on the iron plate, and, what was most singular, when the inscription was indented in the gun cotton it was indented in the iron plate, and when the inscription was raised on the surface of the gun cotton it was reproduced raised on the surface of the iron plate. In experimentally investigating this phenomenon I eventually soaked several cylinders in water, so that I could bore them without danger, and then bored holes of various diameters and depths in them, until in the last instance I bored a vertical hole an inch and three quarters in diameter completely through the cylinder. These wet cylinders were each placed on a similar iron plate, a similar dry disk was placed on each as a primer, and they were successively fired, when it was found that the deeper and wider the hole in the gun cotton the deeper and wider were the holes produced in the iron plate, until when the completely perforated gun-cotton cylinder, from which at least half of the weight of explosive had been removed by the boring, was fired, the iron plate was found to be completely perforated.

Advantage was taken of this action of the rapidly moving molecules to produce some beautiful effects by interposing laces, coins, leaves from the trees, and stencils with various devices cut in them between the base of the gun cotton and the iron plate, for after the detonation of the gun cotton the objects were found to be reproduced upon the iron with the utmost fidelity and in their most delicate parts, and the impressions were raised upon the iron as the objects had been before the explosion.

In one instance a disk of gun cotton was placed in a tin which had been used in canning peas. The disk was covered with water so as to be completely immersed in it, PSM V56 D0468 Maple leaf reproduced on iron plate.pngMaple Leaf reproduced on Iron Plate. and a second dry disk, with which to fire it, was placed upon the wet one. The face of the can resting in contact with the iron plate was originally the top of the can, through which the vegetable had been introduced, and it was consequently grooved where the cover was soldered on, and it also had an irregular drop of solder over the vent hole, the solder being raised, therefore, above the general level of the face. On firing, the can was completely volatilized or comminuted as usual, but the face of the can was reproduced in every feature and with the original values of the surface, the groove being indented in the iron, and the solder being raised above the rest of the impression.

In another instance a disk of gun cotton three inches in diameter was placed in a tin can five inches in diameter, and the can, which had a smooth bottom, placed on the face of an iron I-beam. The can was filled with water so as to just cover the gun cotton, a second dry gun-cotton disk was placed on the wet disk of a primer, both being in constant contact with one side of the can, and the system detonated. As a result the can and water disappeared and the face of the beam was torn off, but on recovering the pieces and matching them it was found that not only was the smooth base of the gun cotton and the face of the can reproduced in the iron, but in the space between the gun cotton and the side of the can, occupied by the water, three distinct sets of waves were produced, having an increasing amplitude from the center proceeding outward. It is evident that many curious effects can be produced with explosive substances, and I do not doubt that useful applications will be found through a close study of the phenomena attending them.

 

A YEAR'S PROGRESS IN THE KLONDIKE.
By Prof. ANGELO HEILPRIN.

TWO years ago the difficulties of reaching the Klondike were thought to be of such a nature as to preclude the probability or even possibility of Dawson ever becoming a place of permanent habitation. The trials of the Chilkoot and White Passes were exploited in magazine and journal from one end of the continent almost to the other, and the wrecks of humanity, and particularly of the thousands of beasts that lay scattered along the trail—the tribute to the Sahara turned to shame—were appealed to as grim testimony of the almost insuperable barrier which separated man from the object of his search. To-day, and since July 6th of the past year (1899), a steam railway traverses the full forty-two miles of the White Pass trail, and the traveler enjoys the beauties of the subarctic landscape in much the way that he enjoys the trip through the Alleghany Mountains in the East, or of the prairies in the West. Deposited at Bennett, on Lake Bennett, at virtually the head of navigation of the mighty Yukon River (otherwise known as the Lewes), he engages passage on one of several commodious steamers heading down stream or northward, and with one change—at the Miles Cañon and White Horse Rapids, where there is a five-mile portage—reaches Dawson after a voyage, delightful in its change of scene and novelty of experience, of from four to six days. It is a fact, therefore, that with a strict timing of departures the traveler from New York may make the journey to Dawson in summer time in twelve days, and exceptionally even in less; and the journey has indeed been made in eleven days and a half. Such is the change which the effort of less than two years has accomplished.

The Dawson of 1899 is no longer the Dawson of 1898, and much less that of the year previous. The thousands of bateaux that were formerly lined up against the river front, in rows six

    Note.—Acknowledgment is here made to Mr. E. A. Hegg for the use of most of the photographs accompanying this article.

  1. Van Nostrand's Engineering Magazine, vol. xxxii, pp. 1-9, 1885.