This was a crude way of mounting the gun, and it was Garros’s mechanician who worked out the method of gearing up the machine-gun so that it shot its 600 bullets between the revolutions of the propeller. This enabled the so-called single-seater scout tractors, with propeller in front, to fly armed with a machine-gun mounted over the hood of the engine, directly in front of the aviator. It was also the beginning of the use of the aeroplane as a fighter in aerial duels and in contact patrol of later days when it descended to attack troops in the trenches and trains on the tracks. January 1, 1915, was the date of mounting the first Lewis machine-gun on a Nieuport aeroplane to shoot over the propeller. The Germans copied this with their Parabellum light gun, but it was not till July, 1915, that the German Fokker first appeared with a synchronized machine-gun mounted on it. Since a propeller revolves 1,400 times a minute, a blade passes the nose of the gun 2,800 times a minute, and the machine-guns were geared to shoot about 400 shots a minute, so that one shot passes through to every seven strokes of the propeller-blade. Sometimes, however, as many as two guns were synchronized to shoot through the same propeller. A push-button on the steering-bar fires the gun while the pilot keeps his eye on the enemy through the telescope in front of him. The Lewis gun is an air-cooled, gas-operated, magazine-fed gun, weighing 26 pounds with the jacket and 18 pounds without. The facility with which the gun can be manœuvred into any position or angle makes it a very efficient aeroplane gun. The ability of this gun to function automatically, and the speed with which it operates, is due to the use of a detachable drum-shaped, rotating magazine which holds 47 or 97 cartridges each. When the magazine is placed in position it needs no more attention until all the cartridges are empty, when the magazine is snatched off and another is stuck on. This gun is the invention of Colonel Isaac Lewis, a retired American army officer. The Vickers is an English gun, belt-fed, water-cooled, recoil-operated. It can shoot from 300 to 500 shots a minute. Since all the shells are in a belt it can be fired continuously until the 500 shots have been used up. Its water-cooled devices were dispensed with on the aeroplanes. The German Maxim is similar to the Vickers. The Lewis shoots .33 and Vickers and Maxim .30 ammunition. In the beginning of the war the Colt gas-operated gun was also used on aeroplanes, as were also the Hotchkiss and Benet-Mercier. The first gun shooting 400 shots a minute was similar to the Vickers. Owing to the ease with which the cotton-belts containing the cartridges on Vickers guns jam, it was used only for fixed positions in front, whereas the Lewis was employed in the observer’s nacelle and other positions which required sudden change in the aim. As many as half a dozen machine-guns were mounted on some of the large bombers in the last days of the war.