Simplification of the chassis is becoming evident in the latest forms of all military aëroplanes, the reduction of weight in this portion of the apparatus being important. To Mr. Farman belongs the credit of having first applied to his aëroplane the now famous Gnome motor, in which seven or more cylinders revolve. It can truly be said that the influence of this motor on facilitating flight generally, and very particularly military aviation, has been nothing short of prodigious. The aëroplane, like the airship, had to wait for the light petroleum motor. Its advent made flight possible, but achievement in flight would have been comparatively small had it not been for the welcome appearance of a motor specially adapted to the purpose. The early forms of aëroplane engines in which the cylinders were fixed had proved to be quite unreliable owing to the high speeds at which the engines had to work. Overheating, loss of power, and stopping were frequent occurrences. The water-cooling and air-cooling systems introduced were equally inefficient. The very fact that the cylinders of the Gnome motor revolved effected the desideratum of automatic cooling, and also gave a smooth, even thrust to the propeller. If the aëroplanes in the present war were flying over the enemy’s lines with old-fashioned engines, they would be dropping down into hostile hands as quickly as dying flies from the ceiling on the first winter days. After the introduction of the Gnome motor, it was quickly realised that the speeds secured by its use gave the aëroplane a stability that was absent in the more slowly moving machines. Winds that were the bugbear of the aëroplanists could then be combated, and the aëroplane ceased to be the fine-weather machine. Heights could then be climbed that a little while before were undreamt of. It is said that there are some disadvantages in the case of revolving cylinders--that they have been known to produce a gyroscopic effect that has upset the machine. This, however, is a somewhat doubtful point. It may be urged that the greater silence of motors with fixed cylinders is an advantage in war. This may sometimes be so, and it is quite possible that for offensive aëroplanes a special type of motor may be in the future evolved. To return to the other features of the Farman machine. The plan he adopted in his racing machines of making the upper plane larger than the lower one was a valuable step in speed-producing machines. The records won by Mr. Farman with his machines alone testify to its efficiency. Often he has held the world’s records of distance, duration, and height, wrestling, indeed, for these with the Blériot monoplane.