This photograph, taken by a passenger in a Grahame-White biplane, gives an excellent idea of the view that may be obtained from a machine in flight. Another aeroplane is flying past the enclosures, and there is a Midland railway train in the distance.] As soon as they became reliable, and could be used in war, aeroplanes and airships were pressed into service as scouts--their task being to ascend, spy out the land below, and return with news to their starting-points. That was the first conception of their use, and War Departments looked no farther. But when machines were built in numbers, and air fleets began to form, strategists saw the complications that would ensue. If A has a fleet of aircraft and B also, and A and B are at war, then the aim of each will be to hamper the other’s air-scouts, and destroy them whenever possible. Here, again, is the theory of move and counter-move. The air-scout, flying above an army, may see its secret at a glance; therefore steps must be taken to keep him off, to drive him away, to blow him to pieces and all of his kind. This may be done with a cannon from the ground, but the method is not certain. Special guns have been built which will point into the air, can be sighted quickly, and will fire a shell to a great height. If an aircraft comes within range of them, and the gunner has time to aim correctly, a bursting shell may bring the machine to ground. But there are the “ifs” to be remembered. The scout--favoured by a clear day and using his own judgment--may be able to do his spying without venturing within range of a land gun; and, even should he come into firing distance, he may be shot at and missed. Such guns are valuable, of course--mounted upon motor-cars for speedy transport from place to place, and used also to guard fortifications, and against aerial foes by a ship at sea. Other guns are possible, besides those which fire shells. Attention has been directed to the feasibility of using a form of vortex-gun. This is a weapon rather like a huge air-gun. It compresses a charge of air and discharges it at a high velocity in a whirling vortex or ring. This, invisible but immensely destructive, strikes its target like a cyclone, and has been known--even with the use of an experimental gun--to tear up fences at a distance of several hundred yards. If such a gun was discharged at an aircraft, and the aim was accurate, it is argued that the machine would be hurled over and wrecked by the force of the artificial hurricane.