In operation, this wing-warping device was simple. When the airman discovered that his machine was tilting over one side, owing to a sudden inequality in wind pressure, he quickly warped down the plane-ends on the side of the biplane that was depressed. The result was that there was increased wind-pressure under the plane-ends warped down, thus tending to force the machine back again upon an even keel. The pilot who distinguished himself greatly at Rheims, when flying the Wright biplane, was Lefevre; but this daring airman was, unfortunately, killed shortly afterwards at Juvisy, when testing a new machine. At Rheims he circled in the air, and effected sharp turns, in an altogether remarkable way, demonstrating an absolutely complete control over his machine. So impressed were the representatives of the French Government by the performance of the Wright biplane, that they ordered several machines for military use. This represented their first definite order for aeroplanes for war purposes. The chief drawback of the Wright biplane, in comparison with other machines flown at this time, was that it needed to make a start into the air from a launching rail, as has previously been mentioned. The advantage of this system of starting—in which a weight, dropped from a derrick, gave the aeroplane its initial impetus along the rail—was that the machine could be fitted with a lower-powered engine. But the disadvantages were obvious. Were an involuntary descent made at a point some distance away from the machine’s rail, it had to be carted back to the starting-point, or a rail and derrick brought to the place where it lay. However, the French Government did not regard any aeroplanes at this time as representing serviceable war weapons. They took the wise view that they were purely instructional craft, upon which military airmen could gain experience, and so fit themselves for the use of the more perfect machines which were likely to be evolved as time went on. After describing the Wright biplane, we may now consider the Voisin machine. This aeroplane represented an improvement upon the type first piloted by Farman at Issy-les-Moulineaux. It had two main supporting planes, like those of the Wright biplane, fitted one above another. In front of the main-planes was a single horizontal elevating plane. At the rear of the biplane was a large cellular stabilising tail, made up of horizontal and vertical planes, and resembling a box-kite. In the centre of this cellular tail was the rudder, a single vertical plane. Instead of adopting a wing-warping device, for maintaining lateral stability, the Voisin brothers fitted vertical planes, or curtains as they were called, between their main-planes. These, when the machine was in flight, resisted any sideway roll and, in conjunction with movements of the rudder, gave the aeroplane a certain amount of automatic stability.