B is a copper case to contain one hundred or more pounds of powder; C a cork cushion to give the whole Torpedo such a buoyancy, that it will be only from two to three pounds heavier than salt water. To ascertain such weight, when it is charged with powder and the lock screwed on, it is put into a large tub of sea water. C is to have fifteen or twenty inch-holes bored in its sides and top, to let the water rush in and the air out, otherwise, the air would prevent its immediately sinking. A is a cylindric brass box, about seven inches diameter and two inches deep, in which there is a gun-lock with a barrel two inches long, to receive a charge of powder and a wad, which charge is fired into the powder of the case B. In the brass box A there is also a piece of clockwork moved by a spring, which being wound up and set, will let the lock strike fire in any number of minutes which may be determined within one hour. K is a small line fixed to a pin, which pin holds the clockwork inactive; the instant the pin is withdrawn the clockwork begins to move, and the explosion will take place in one, two, three, or any number of minutes for which it has been set; the whole is so made as to be perfectly tight and keep out the water, although under a pressure of twenty-five or thirty perpendicular feet. D is a pine box two feet long, six or eight inches square, filled with cork; it is ten or fifteen pounds lighter than water, and floats on the surface; the line from it to the Torpedo is the suspending line, which must be of a length in proportion to the estimated draft of water of the vessel to be attacked; vessels of a certain number of guns usually draw within a few feet of the same draft of water; the suspending line should be from four to eight feet longer than the greatest draft of the vessel, that it may bend round the curve of her side, and lay the Torpedo near her keel. From the Torpedo and the float D, two lines, each twenty feet long, are united at E, from thence one line goes to the harpoon, the total length of the line from the Torpedo to the harpoon being about fifty feet, according to the length of the vessel to be attacked, will, when the ship is harpooned in the bow, bring the Torpedo under her bottom near midship. See the harpoon. It is a round piece of iron, half an inch diameter and two feet long, the butt one inch diameter, the exact calibre of the harpoon-gun; in the head of the harpoon there is an eye, the point six inches long is barbed, the line of the Torpedo is spliced into the eye of the harpoon, a small iron or tough copper link runs on the shaft of the harpoon, to the link the Torpedo-line is also tied, and at such a distance, that when the harpoon is in the gun it will form a loop as at H, but when fired, the link will slide along to the butt of the harpoon, and, holding the rope and harpoon parallel to each other, the rope will act like a tail or rod to a rocket, and guide it straight; without this precaution, the butt of