Page:Popular Science Monthly Volume 58.djvu/505

Rh charge for shells. A large number of explosive compounds have been submitted by various inventors and tested by the Ordnance Department of the United States Army at the Sandy Hook Proving Grounds.

Some of the explosive compounds submitted have given very satisfactory results. Perhaps half a dozen of them would serve fairly well, if nothing better could be found. The Government, however, has placed its standard of excellence very high, with the hope of finding, if possible, something better than is possessed by other countries.

The United States Government was one of the last to adopt a smokeless powder, notwithstanding the fact that it was one of the first to experiment with these new explosives. But the Departments then having the matter in charge were very conservative, taking nothing for granted, were uninfluenced by the example of other countries and were determined that nothing but the best would be good enough for Uncle Sam. The result is that this Government to-day possesses a smokeless powder superior to that adopted by any other country. The same policy has been manifested in the search for a high explosive suitable as a bursting charge for shells.

The tests through which a high explosive must pass before there is the least hope of its meeting the requirements of the Government are very severe. The inventive Yankee, having an ambition to serve the Government by producing for its use a satisfactory high explosive, has u difficult task before him. In the first place, the compound must be perfectly stable, and to determine this it is submitted to a severe heat test for a period of fifteen minutes. If it fails to stand this test it is condemned at once, and goes no further. If it passes the heat test satisfactorily, a quantity is then placed under a falling weight or hammer to test its sensitiveness or its ability to resist shock. This is determined by the height from which it is necessary for the hammer to fall in order to explode the material. If the explosive proves sufficiently insensitive to indicate that it will stand the impact or shock of penetrating armor plate, it is then tested to determine its explosive power. A forged steel armor-piercing shell is filled with the material and armed with a very powerful exploder, which is set off by electricity. The force of the explosive is shown by the number and character of the fragments. Small shells are burst for fragmentation in a steel-walled chamber; larger shells are buried in the sand and exploded, the fragments being recovered by sifting the sand.

If the number of fragments indicates a sufficiently high explosive power, an armor-piercing shell is filled with the compound and fired through a nickel steel plate, so thick as to almost stop the shell in passing through, leaving just velocity enough to carry it a few feet into a sand butt back of the plate, where it may be dug out and recovered, provided the explosive proves to be sufficiently insensitive to