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Page:Popular Science Monthly Volume 21.djvu/802

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THE POPULAR SCIENCE MONTHLY.

these tests tend to show that it possesses in a high degree the elements desired in the ideal high explosive for military purposes, if not for commercial use.

So much difficulty was encountered in the first attempts at the construction of a suitable primer for its explosion, that it seemed doubtful whether it would ever be a practicable material, as it was thought that nitro-glycerine must be used to accomplish the desired result. Subsequent experiments conducted in this country have shown, however, that a dry gun-cotton fuse with a fulminate cap containing twenty-five grains will fire the gelatine with ease and certainty, even when unconfined. The problem so long confronting the manufacturer of explosives would seem to be nearly solved: the requisites of great power in small compass, of permanency when subjected to tropical heat, of ease of firing when but slightly confined, of safety from the explosion of neighboring masses of the same or on being struck by a projectile, and of not being affected injuriously by water, all seem to be fulfilled by this agent in a manner more complete than by any other.

If it should be found that a long-continued exposure to heat tends to produce decomposition, as may prove to be the case, greater care in the preparation of the materials from which it is manufactured will probably overcome this difficulty, and it will then bid fair to supersede gun-cotton for very many purposes, if it does not altogether take its place.

Constant allusion has been made to the use of fulminate of mercury as an agent for the firing of other explosives. It is prepared by dissolving mercury in nitric acid, and then mixing this solution with alcohol, in a vessel placed in a hot-water bath. Dense white fumes soon arise from the agitated liquid, until finally, the disturbance having subsided, the bottom of the vessel is found covered with a gray powder, which is afterward thoroughly washed. This gray powder is the fulminate used in the caps and cartridges familiar to sportsmen, as well as in the primers for cannon and the fuses for the explosion of a quantity of gunpowder or other explosives. Being harmless when wet, it is usually kept and handled in that condition. Generally speaking, electricity is the agent by means of which the fulminate is ignited; the fuse for this purpose is ordinarily constructed as follows: A brass or copper cylinder, about half an inch in diameter, closed at one end, is partially filled with the desired quantity of the wet fulminate; when this has become thoroughly dry, a wooden plug closing the entrance is inserted; in this plug are two holes, through each of which passes an insulated copper wire with bared ends, which project a short distance above the surface of the plug and are connected by a very small wire composed of an alloy of platinum and silver; around this wire, or bridge, as it is called, is twisted a small wisp of dry guncotton, which, when the plug is in place, comes in contact with the ful-