This condition will soon manifest itself, and be corrected by the experimenter; but there is another difficulty which is not so easy to discover and so quick to remedy, and that is the swing of the legs the moment the operator leaves the ground. The experimenter learns, after many attempts, that gliding is a matter of a few feet only, and he anticipates landing too soon, and the moment he leaps from the ground the legs are swung forwardly ready to alight. This is done unconsciously, just as a jumper swings his legs forwardly in the act of alighting. Such a motion naturally disturbs the fore and aft stability of the gliding machine, by tilting up the forward margin, and it banks against the air, instead of gliding. The constant fear of all gliders is, that the machine will point downwardly, and his motion, as well as the position of the body, tend to shoot it upwardly, instead. CHAPTER IX AEROPLANE CONSTRUCTION As may be inferred from the foregoing statements, there are no definite rules for the construction of either type of flying machine, as the flying models vary to such an extent that it is difficult to take either of them as a model to represent the preferred type of construction. LATERAL, AND FORE AND AFT.--The term lateral should be understood, as applied to aeroplanes. It is always used to designate the direction at right angles to the movement of the machine. Fore and aft is a marine term meaning lengthwise, or from front to rear, hence is always at right angles to the lateral direction. The term transverse is equivalent to lateral, in flying machine parlance, but there is this distinction: Transverse has reference to a machine or object which, like the main planes of an aeroplane, are broader, (that is,--from end to end) than their length, (from front to rear). On the other hand, lateral has reference to side branches, as, for instance, the monoplane wings, which branch out from the sides of the fore and aft body. STABILITY AND STABILIZATION.--These terms constantly appear in describing machines and their operations. If the flying structure, whatever it may be, has means whereby it is kept from rocking from side to side, it has stability, which is usually designated as lateral stability. The mechanism for doing this is called a stabilizer. THE WRIGHT SYSTEM.--The Wright machine has reference solely to the matter of laterally controlling the flying structure, and does not pertain to the form or shape of the planes. In Fig. 49 A designates the upper and lower planes of a Wright machine, with the peculiar rounded ends. The ends of the planes are so arranged that the rear margins may be raised or lowered, independently of the other portions of the planes, which are rigid. This movement is indicated in sketch 1, where the movable part B is, as we might say, hinged along the line C.