Various kinds of bombs are used for dropping from aeroplanes. A simple pattern shown in Fig. 1 consists of a thin spherical shell of steel, containing twelve pounds of tetranitranilin, which is an explosive more powerful than melinite. The stem of the bomb, by which it is handled, has an external screw-thread, and carries a pair of vanes. While in the position shown, the bomb is harmless, but as it drops, the vanes screw themselves up to the top of the stem till they press against the stop. This, by means of a rod passing down the center of the stem, “arms” or prepares the fuse seen at the bottom of the bomb, so that it acts at the slightest touch, even on the wing of another aeroplane. The fuse effects the explosion of the burster by means of a primer of azide of lead, which causes the tetranitranilin to detonate with great violence. The whole bomb weighs twenty-two pounds, and an aeroplane usually carries six of them. The Italians, in their campaign in Tripoli, used similar bombs, but without the special device for rendering the fuse sensitive. These were not a success, as many of them failed to explode in the desert sand, and the Arabs used to collect them and throw them into the Italian trenches at night. STEEL DARTS The Taube aeroplanes, when they flew over Paris, used sometimes to drop steel darts pointed at one end and flattened and feathered at the other, as shown in Fig. 2. These were put up in boxes of a hundred, so that when the box was released from its hook, it turned over and released the darts. “ARROW BULLETS” AND AERIAL TORPEDOES The “arrow bullet” shown in Fig. 3 is a French device; though weighing only three-quarters of an ounce, its peculiar shape enables it to acquire a high velocity, so that it will kill a man when dropped from a height of six hundred yards. An aerial torpedo carried by French aeroplanes for the destruction of Zeppelins is shown in Fig. 4; it contains a powerful charge of explosive and a fuse, to which the suspending-wire is connected. When dropped on a Zeppelin, the needle-pointed torpedo pierces the envelope and gas-chamber, but the wooden cross is arrested and the sudden jerk on the suspending-wire sets the fuse in action, causing the certain destruction of the airship. The torpedo would be too dangerous to handle, but the French have an ingenious device which renders it perfectly safe until it is dropped. MACHINE GUNS IN AIRCRAFT Various attempts have been made to mount machine guns on aeroplanes, but the operator, in his narrow seat, has hardly space to point a machine gun in any direction except straight to his front. The American Curtis machine gun exhibited at Olympia is the most efficient form yet produced, but at present the airman seems to prefer an automatic rifle. Even in the early days of the war, Sir John French was able to report that British airmen had disposed of no less than five of the enemy’s aircraft with this weapon.