Page:Popular Science Monthly Volume 92.djvu/870

 Sinking U-Boats with a Sub-Sea Barrage

The Isham shell, which does not ricochet, is the latest destroyer of the submarine

Bv Robert G. Skerrett

���THE diving shell is the latest thing for attacking hostile submarines. It is the depth- bomb improved and therefore more po- tent. Indeed, in the opinion of many ex- perts the diving shell is the most formida- ble instrument yet devised for battling with the foe's U-boats. It is an out-and-out Ameri- can invention and the climax of years of study and development on the part of its originator, Willard S. Isham.

Of depth-bombs there are several sorts, but of diving shells there are only two kinds — a foreign adaptation of the Isham missile and the Isham projectile, pure and simple. The reason for this is that the French and British governments have been more alive to the merits of the Amer- ican invention than our own ordnance officials, and, as a result, have actually been the first to apply the diving shell to wartime service. We are catching up, however, if reports from Washington can

��be accepted at their face value, and the so-called "non-ricochet shell" is likely soon to have its place in the magazines of all of our destroyers operating in European waters.

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��High-Angle Fire and Its Drawbacks

��High-angle firing makes the shell strike the water at such an angle that it will dive into the sea instead of ricocheting

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��The British and French vessels that are armed to throw their form of diving high-angle fire, the pro- jectile traveling a course much like that of a missile discharged from a mortar. In this way, the shell strikes the water at an angle sufficiently blunt to obviate ricocheting and to insure penetration into the sea. Once the missile has plunged beneath the surface its explosion is auto- matically regulated. The detonating fuse is set to operate at a predetermined sub- mergence as in the case of a depth-bomb. High-angle fire from a moving craft at an object in motion has a number of drawbacks. First, there is the com- paratively protracted flight of the pro-

���The explosion of the Isham shell beneath the surface is regulated automatically by a time fuse set to operate at a certain degree of submergence regardless of hydrostatic pressure

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