THE IjtllUMPH OF THE AEROPLANE 



inquire how the balloonists could ever have expected 

 to accomplish flight at more than a nominal rate of 

 speed; and, on the other hand, it might be asked, 

 naturally enough, how the aviators expected to fly with 

 aeroplane machines at least a thousand times heavier 

 than the air. In reply, the aviators could point to birds 

 and bats as examples of how the apparently impossible 

 is easily accomplished in nature; while the balloonists 

 could simply point to their accomplished flights as 

 practical demonstrations. The aviators could point 

 to no past records of accomplishments, but neverthe- 

 less they had good ground for the faith that was in them, 

 and as we shall see were later to justify their theories 

 by practical demonstrations. 



Everybody is aware that there is an enormous dif- 

 ference in the lifting power of still air and air in motion, 

 and that this power is dependent upon velocity. The 

 difference between the puff of wind that barely lifts 

 a thin sheet of paper from the table, and the tornado 

 that uproots trees and wrecks stone buildings, is one 

 of velocity. Obviously, then, moving air is quite a dif- 

 ferent substance from still air when it comes to dealing 

 with aeronautics. 



One of the most familiar examples of the lifting 

 power of moving air is that of the kite. An ordinary 

 kite is many times heavier than the air and has no 

 more tendency to rise in the air than a corresponding 

 weight of lead under ordinary conditions. Yet this 

 same kite, if held by a string with its surfaces inclined 

 to the wind at a certain angle, will be lifted with a force 

 proportionate to the velocity of the wind and the size of 

 VOL. viL— x« |{ 273 ) 



