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Page:Popular Science Monthly Volume 56.djvu/461

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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

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