become greater than sufficient to stretch the springs 50 per cent of their original length. [p216] In the construction of the equilibrium control wheel it was decided that some arrangement must be secured whereby the wheel would normally be inactive and maintain whatever position it had been set to, and at the same time could be moved by the aviator with one hand, the mere act of grasping it rendering it free to be moved, and whereby it must automatically lock itself in any position in which it might be when the aviator removed his hand from it. The multiplicity of things requiring the attention of the aviator made it desirable that his attention to any one of the important details, whether the engine, the equilibrium, or the steering, should never require more than one hand, thus leaving the other hand free either to hold on to the machine or to control some other detail at the same time. While an irreversible wheel, such as would be secured by the use of a worm and worm-wheel, at first seemed likely to answer the purpose, yet the movement of a worm-wheel by means of a worm is necessarily very slow if it is irreversible, and it here seemed desirable to so arrange the wheel that in case of emergency, of for rising or descending, the aviator could swing the Pénaud tail from its extreme upper position to its extreme lower one by a small motion of his hand, and thus small or large adjustments of the Pénaud tail could be intuitively felt to have been produced without the aviator having to remember how many turns he had made of the wheel. The control of the steering rudder was effected by a steering wheel (51) similar in construction to the equilibrium control wheel (50), a continuous cord (52) passing from the steering wheel through suitable pulleys to either side of the steering rudder (‹r›), springs being interposed in loops in the cord on either side of the steering rudder to give some elasticity to the control apparatus in order to prevent possible danger from the aviator attempting to move the rudder too suddenly. This steering rope passed directly through the steering rudder at the points where it was joined to it; so that, should one side of the cord in any way become entangled with the frame or with its pulleys, the strain produced by the aviator in attempting to move it in the opposite direction would be taken up by the cord and thereby avoid the possibility of destroying the rudder. For even should the cord become entangled on one side, the rudder could be given a slight amount of adjustment through the elasticity of the coiled springs. The design of the combined Pénaud tail and rudder followed very closely that which had been used for the models, and its area of ninety-five square feet on the horizontal surface with a corresponding area of vertical surface bore the same relation to the area of the tail and rudder of the models that the area of the wings of the large machine bore to that of the wings of its prototype.