If a pilot knows, thoroughly well, the kind of country he is flying over, and no difficulty presents itself in finding a landing-place, he can fly comparatively low, if he prefers to do so. By this is meant an altitude of perhaps five or six hundred feet. If the country is difficult, however—that is to say, if fair landing-places are not easy to find—it behoves the airman to attain a considerably greater altitude. Over unfavourable country, from the landing-point of view, an experienced pilot will maintain a height of 2000 feet, or more. He does this because, should his engine fail him, he will have plenty of time to pick out—from a considerable area of country around him—some fairly-suitable descending-point. In the flying contests held last summer, the most expert pilots, such as Beaumont and Vedrines, flew across country at an altitude of about 3000 feet. What influenced them, in doing so, was the knowledge that any wind that is blowing is generally most steady at such altitudes. Once he is able to fly across country, without worrying at all about the control of his machine, the military airman is ready to take up the practical tasks which await him. One of the most interesting experiments, which he will be asked to carry out, is to fly over bodies of troops on the march, and test his powers of observation. It is one thing, of course, to see troops below him, and another to render an accurate report as to their strength and formation. One of the most expert of French military airmen describes, very interestingly, how a reconnoitring officer seeks to render accurate his observations of troops; and his remarks go to prove, very distinctly, that nothing but unremitting practice will create a reliable air-scout—a contention which is made by all experts upon this subject. The strength of columns on the march—when seen from the bird’s-eye view of an aeroplane—should, says this officer, be estimated by comparison, on the airman’s map, with the length of the road along which they are marching. Massed formations of troops should, he adds, be determined according to the open spaces separating the various units. From the airman’s point of view, other clues to the strength of an enemy are the number of waggons, the number of mounted officers (in the case of infantry), and so forth. It will be seen that, although the elevation of an aeroplane gives the observer a unique advantage, reconnoitring from an altitude of, say, 3000 feet is by no means easy work; the point of view is strange, and new rules have to be made, if reliable information is to be forthcoming. With adequate practice, of course, an observer becomes remarkably quick in estimating the import of what he sees below him. Details, which would mean nothing to the novice, frequently tell him the whole story.