A few short years ago flying was in its experimental stage; to-day, though man's conquest of the air is yet a dream unrealised, it has developed enormously and to an amazing degree; to-day, flying is one of the chief factors of this world war, both on sea and land. Upon the Western front alone there are thousands upon thousands of aeroplanes--monoplanes and biplanes--of hundreds of different makes and designs, of varying shapes and many sizes. I have seen giants armed with batteries of swivel guns and others mounting veritable cannon. Here are huge bomb-dropping machines with a vast wing-spread; solid, steady-flying machines for photographic work, and the light, swift-climbing, double-gunned battle-planes, capable of mounting two thousand feet a minute and attaining a speed of two hundred kilometres. Of these last they are building scores a week at a certain factory I visited just outside Paris, and this factory is but one of many. But the men (or rather, youths) who fly these aerial marvels--it is of these rather than the machines that I would tell, since of the machines I can describe little even if I would; but I have watched them hovering unconcernedly (and quite contemptuous of the barking attention of "Archie") above white shrapnel bursts--fleecy, innocent-seeming puffs of smoke that go by the name of "woolly bears." I have seen them turn and hover and swoop, swift and graceful as great eagles. I have watched master-pilots of both armies, English and French, perform soul-shaking gyrations high in air, feats quite impossible hitherto and never attempted until lately. There is now a course of aerial gymnastics which every flier must pass successfully before he may call himself a "chasing" pilot; and, from what I have observed, it would seem that to become a pilot one must be either all nerve or possess no nerve at all. Conceive a biplane, thousands of feet aloft, suddenly flinging its nose up and beginning to climb vertically as if intending to loop the loop; conceive of its pausing suddenly and remaining, for perhaps a full minute, poised thus upon its tail--absolutely perpendicular. Then, the engines switched off, conceive of it falling helplessly, tail first, reversing suddenly and plunging earthwards, spinning giddily round and round very like the helpless flutter of a falling leaf. Then suddenly, the engine roars again, the twisting, fluttering, dead thing becomes instinct with life, rights itself majestically on flashing pinions, swoops down in swift and headlong course, and, turning, mounts the wind and soars up and up as light, as graceful, as any bird.