soil could escape the record of the camera when read by the aid of a magnifying glass. Contact patrol, or reports by low-flying aeroplanes on the exact position of the advancing infantry, came later, and supplemented the use of the telephone, which was liable to be destroyed by shell-fire. Our contact patrols saved us from a world of those most distressing of casualties, the losses inflicted on troops by their own guns. Serious battle in the air, which was engaged on no large scale until the second year of the war, was, in its essence, an attempt to put out the eyes of the other side. In the early days officers often took a revolver, a carbine, or a rifle, into the air with them, but machines designed expressly for fighting, and armed with Lewis or Vickers guns, did not appear in force until it became necessary to counter the attacks made by the Fokker on our observation machines. Then began that long series of dramatic combats, splendid in many of its episodes, which fascinated the attention of the public, and almost excluded from notice the humbler, but not less essential, and not less dangerous, duties of those whose main business it was to observe. Lastly, the offensive powers of aircraft have been so rapidly developed, especially during the latest period of the war, that it was only the coming of the armistice that saved mankind from a hurricane of slaughter. In 1914 a few small bombs were carried by officers into the air, and were gingerly dropped over the side of the machine. Accuracy of aim was impossible. In the large modern bombing machine the heavier bombs weigh almost three-quarters of a ton; they are mechanically released from the rack on which they are hung, and when the machine is flying level, at a known pace and height, good practice can be made, by the aid of an adjustable instrument, on any target. Even more desolating in its effect is the work done by low-flying aeroplanes, armed with machine-guns, against enemy troops on the march. Raids on the enemy communications, for the destruction of supplies and the cutting off of reinforcements, played a great part in the later phases of the war; and long-distance raids over enemy centres served to bring the civil population into sympathy with the sufferings of the army.