[Illustration: SMOKELESS POWDERS. In the bottle is indurite in flake grains. The larger grains are cylindrical and hexagonal multiperforated United States army grains. The bent grain in the foreground, looking like a piece of rubber tubing, is a grain of Maxim powder with a single canal. The flat strips in the foreground on the left are grains of the French B. N. powder. The flat strips in the foreground on the right are grains of the United States navy “pyrocellulose” powder.] Mercury fulminate is made by dissolving mercury in nitric acid and pouring the solution thus produced into alcohol, when a violent reaction takes place and the fulminate is deposited as a crystalline gray powder. This powder is loaded in copper cases and, after drying, it is primed with dry-mealed gun cotton, the mouth of the case being closed with a sulphur-glass plug, through which pass two copper leading wires joined by a bridge of platinum-iridium wire, two one-thousandths of an inch in diameter, which becomes heated to incandescence when an electric current is sent through it. This device is what is known as the naval detonator. Mercury fulminate is so employed because it is the most violent of all explosives in common use, and exerts a pressure of forty-eight thousand atmospheres when fired in contact. Although the naval detonator contains but thirty-five grains of mercury fulminate, yet it will rupture stout iron and heavy tin torpedo cases when fired suspended in them, it will rend thick blocks of wood when placed in a hole and fired within them, and it will even pierce holes through plates of the finest wrought iron one-sixteenth inch in thickness if only the base of the detonator is in contact with the plate, and this has been used as a test of their efficiency. Its force is markedly shown by firing one in a stout iron cylinder filled with water and closed tightly, when the cylinder is blown into a shredded sphere. When used to detonate gun cotton, either when confined or in the open, the detonator is placed in the hole which has been molded in the center of the gun cotton disk or block, so that it shall be in close contact with the gun cotton. I have found that perfectly dry compressed gun cotton is detonated by 2.83 grains of mercury fulminate; but as a torpedo attack is necessarily in the nature of a forlorn hope and should be provided with every possible provision against failure, and since if the detonator fails the attack fails, the naval detonator is supplied with thirty-five grains, so as to give a large coefficient of assurance. [Illustration: BLENDING MACHINE FOR CORDITE.] [Illustration: CARTRIDGE OF CORDITE SMOKELESS POWDER. Charge for 6-inch 2 F gun, 13 pounds, 4 ounces. Cords, 22¾ inches long, 3 inches in diameter.]