THE CONQUEST OF THE AIR. 355 



fold. If the surface is cambered, this capacity increases seven to 

 eight fold. Only these discoveries have made flight possible. It 

 may be explained as follows : — We can set up a continuous rela- 

 tive force P only if we keep particles of air continually on the 

 move. In the case of an inclined plane we set more particles of 

 air in motion than with surfaces directed vertically downwards, 

 hence the greater carrying capacity. The cambered surface is 

 even better than the inclined plane without increasing materially 

 the air resistance. We may express the carrying effect by a 

 formula similar to the one for the air resistance. 



We have P = o.56 KFW'-, where W = lateral velocity. The 

 force T, necessary to move the plane laterally, is about ^ of P, 

 or 



T = o.o7 KFW* and for K = 0.125 

 we get 



PxW 



HP = 



76 

 PxW 



or as P = G = weight. 



8x76 



G X 20 G 608 



HP whence = — - 



608 HP W 



G 



For = 15, i-s- fof 15 kgs- per square-metre surface we get 



HP 



G 608 



=15= or 



HP W 



608 

 W= — = 40.5 metres per second. 



15 

 The carrying capacity of i square-metre is then found as 



follows : — 



P = 0.56 X o. I25FW■- 

 P=o.07x Px W^ 



G 



but P = G = weight, hence — = .07 W^ 



F 

 with W = 40. 5 metres per second (91 miles per hour) 



G ., , 



-p =0.7x40.5 =115 kgs. 



Even with W = 20 m/ sec. (45 miles per hour) the carrying capa- 

 city is— =.07x20-2^28 kgs. per square-metre, which is a de- 

 cided progress over the vertically downward directed motion. 



The means for rapidly moving cambered surfaces have made 

 flying possible. 



A high speed is directly desired, as we have seen. If we add 

 one or more inclined surfaces, which are rapidly moved in order 

 to produce the necessary reactive force, i.e. which will give the 



