NAVIGATING THE AIR 



having thin, fixed surfaces, slightly inclined to the line of 

 motion, and supported by the upward pressure of the 

 air due to the forward movement. 



Everyone will remember the distance to which a skil- 

 ful juggler can project an ordinary playing-card by 

 giving it a certain inclination in throwing. It will 

 travel upward or on a level, and continue this direction 

 until the force of the movement of throwing is exhausted. 

 Obviously, if this force were self-contained in the card — 

 if it could continue rotating and moving forward — ^it 

 could fly indefinitely. Henson had studied and ex- 

 perimented with these miniature aeroplanes, and was 

 convinced that if the same principle that governed their 

 flight were to be applied to larger machines, practical 

 flying-machines could be made. 



" If any light and flat, or nearly flat, article," he wrote, 

 "be projected edgeways in a slightly incKned position, 

 the same will rise on the air till the force exerted is ex- 

 pended, when the article so thrown or projected will 

 descend; and it will readily be conceived that if the 

 article possessed in itself a continuous power or force 

 equal to that used in throwing or projecting it, the article 

 would continue to ascend so long as the forward part of 

 the surface was upward in respect to its hinder part, and 

 that such article, when the power was stopped, or when 

 the inclination was recovered, would descend by gravity 

 only if the power was stopped, or by gravity, aided by 

 the force of the power contained in the article, if the 

 power be contained, thus imitating the flight of a bird." 



But when Henson attempted to fly in his elaborately 

 planned and constructed flying-machine, it proved a 



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