THE CONQUEST OF THE AIR 93 



they could be warped a little, throwing the front edges up or 

 down as necessity required. In all experiments with the glider 

 the chief difficulty encountered was found to be the balancing 

 of the plane. The sea of air in which the pilot launches his 

 glider is not a calm sea but is full of waves and cross-currents. 

 Every large obstruction like a hill on the surface of the earth 

 throws the wind up into a billow. The wind does not blow 

 steadily but in gusts and flaws that come first from one point 

 of the compass and then from another. Lillienthal had 



FIG. 39. Langley's aeroplane 



endeavored to balance his machine by movements of his body. 

 He supported himself in his machine by resting on the frame 

 with the supports under his arms, leaving his body from the 

 shoulders down free to swing in any direction. If a gust of wind 

 tended to lift one wing of his machine he threw his body over 

 toward that wing, so shifting his weight as to bring the wing back 

 again into its horizontal position. In such a position his body 

 offered large surface to the wind that tended to retard the flying 

 of the machine. The Wright brothers were accustomed to lie 

 on the lower plane, thus reducing the air resistance of their 

 bodies, and near at hand were the levers that controlled the 



