THE CONQUEST OF THE AIR 87 



These are only a few of the more famous persons who all 

 down through the centuries have tried to fly by crude wings 

 operated by their own weak muscular energy. They were 

 doomed to failure, for it is estimated that a man can exert such 

 continuous muscular energy only to the extent of a third of a 

 horse-power (see p. 183) while it would take some two horse- 

 power to operate wings with sufficient power to lift him from the 

 ground. 



There followed these first foolhardy attempts at flight, with- 

 out knowing anything of the principles underlying the process, 

 a period in which an attempt was made to get at the facts and 

 discover scientifically the principles. Sir George Cayley, an 

 English engineer and scientist, as a result of his study and experi- 

 ments, suggested the use of a steam engine to furnish motive 

 power for the flying machine and that the engine be made to 

 drive revolving propellers. He further advised that the wing 

 planes be curved from front to back instead of being flat, so as 

 to increase the lifting power. He predicted that a tail plane 

 would add materially to the stability of the machine. These 

 suggestions, published in Nicholson's Journal in 1809-10, were 

 not incorporated into an actual flying machine by Gayley. It 

 was not until Henson and Stringfellow, an Englishman and an 

 Australian respectively, built a model aeroplane in 1845 that 

 any of them took concrete form. 



But while Cayley did not build a flying machine he did some- 

 thing that, at that stage of the development of air craft, was more 

 important. About 1797 he built a glider, as we should call the 

 appliance now, and experimented with it. It was really a large, 

 light plane like a kite but not kite-shaped. Cayley thought 

 that, if you can raise a kite, a small plane with its attached 

 string and tail, into the air, a big plane might raise itself and a 

 man if he would run into the wind with it, holding it tipped up 

 slightly at the front so the wind could get under it and exert 

 its power. Cayley 's glider actually worked and lifted him from 

 the ground, carrying him some distance. 



