The United States government had, several years previously, adopted the multi-perforated smokeless cannon-powder invented by me. This form of grain rendered it possible to use a pure nitro-cellulose smokeless powder in large guns, because it greatly reduced the initial area of combustion in proportion to the mass, while as the combustion progressed this condition was reversed and a very large area was presented to the flame of combustion in proportion to the mass. Consequently, the initial pressure in the gun was much reduced, while greater pressure was maintained behind the projectile in its flight through the gun than could be obtained by any other form of grain. This made possible the attainment of a very high velocity, with a comparatively low initial pressure and, consequently, with comparatively small strain upon the gun. For this reason, and because of the low heat in the combustion of pure nitro-cellulose powder, the erosive action upon the gun was reduced to a minimum.
I invented another and a special form of multi-perforated grain by means of which a yet lower initial pressure for a given density of loading was secured, the rate of combustion being still more highly accelerated.
Believing that the advantages of projectiles of great size, carrying a very large bursting charge, could be better illustrated by a gun of extraordinary caliber, I designed a cannon having a caliber of twenty-four inches, but having a weight of only 43 tons, the weight and length of the gun being the same as the British 12-inch 43-ton gun. This gun was designed to throw a semi-armor-piercing projectile weighing 1,700 pounds, and carrying an explosive charge of 1,000 pounds, the total weight of the projectile being 2,700 pounds. While the projectile was not designed to pierce heavy armor, it was capable of penetrating the decks and sides of light-armored cruisers and deep into earth or concrete for the destruction of forts. It was a veritable aërial torpedo. By means of the special form of multi-perforated smokeless powder designed for this gun, the huge projectile could be thrown to a distance of nine miles with the gun at maximum elevation, and still with a comparatively low chamber pressure.
The projectile was provided with a safety delay-action detonating fuse, designed to explode it after having penetrated the object struck, thereby securing the maximum destructive effects.
It is reported that the Germans have made a huge howitzer weighing 45 tons, having a caliber of 23-1/2 inches, which also is capable of throwing a projectile weighing more than a ton to a distance of nine miles.
The drawings used in my lecture were published in the Journal of the Royal United Service Institution, April, 1898, and re-published in many scientific and engineering magazines, and in newspapers both here and abroad. The descriptions of this gun and projectile were illustrated, as was the manner of its employment for the destruction of the kinds of forts destroyed by the Germans at Liège and Namur.
The use of high explosives in big armor-piercing projectiles is now universal, but on the publication of my lecture in 1897 I was subjected to much criticism, especially in some of the London newspapers, whose editors took issue with me as to the practicability of throwing large bursting charges of high explosives from high-power guns. Prior to that time the only success achieved in throwing large charges of high explosives was by use of the Zalinski pneumatic dynamite gun, a battery of which had been made and mounted at great expense at Sandy Hook. These air-guns imparted a maximum velocity of only about 600 feet per second to the projectile. The maximum charge was 600 pounds of nitro-gelatin. The projectile had no penetrating power whatsoever, and was designed to go off on impact.
My proposition to throw large charges of a high explosive from a big gun, at high velocity, using a propelling charge of gunpowder, appeared to many to be a very hare-brained intention indeed, to say nothing of shooting it through armor and exploding it behind the plate.
On my return to America in 1898, I laid the matter before General A. R. Buffington, Chief of the Bureau of Ordnance, United States Army, and Admiral Charles O'Neil, Chief of the Bureau of Ordnance, United States Navy. General Buffington sent me to Sandy Hook, where my new explosive, Maximite, was subjected to a very thorough trial. The first 12-inch projectile charged with it was buried in sand in an armor-cased cellar, and exploded. More than seven thousand fragments of the projectile were recovered, being sifted out of the sand. Twelve-inch projectiles charged with Maximite were repeatedly fired through 12-inch armor-plate without exploding. Later, similar projectiles, armed with a fuse, were fired through the same plate and were exploded behind the plate. Although Maximite was fifty per cent. stronger than ordinary dynamite, yet it was so insensitive to shock as to be incapable of being exploded without the use of a very strong detonator. Maximite was the first high explosive successfully to be fired through heavy armor-plate, and exploded behind the plate, with a delay-action fuse. The fuse employed at that time was the invention of an army officer. Later, my fuse was subjected to a very long series of tests, and it was finally adopted in 1907 as the service detonating fuse by the United States Navy.
If Uncle Sam would listen with an understanding mind to the language of the big guns now speaking on land and sea, he would immediately build a large number of huge howitzers. He would build a large number of good roads, capable of standing the tread of these howitzers. He would build as well a goodly number of battle-cruisers, as big and as fast as any afloat in foreign seas, and armed with guns ranging as far as the guns of any foreign power.