GLIDING 



19 



says, " Nearly one square foot for each pound 

 weight." But it has in view big machines only. 

 When we go to the various creatures that fly, weigh 

 them and measure their surfaces, we get most 

 diverse results. The big flyers, we find, have small 

 wings, the small flyers big ones, if difference in weight 

 is allowed for. Compared with a gnat or a butterfly 

 a Stork has a very small supporting surface, a small 

 one even when he is compared with a Swallow. 

 When M. de Lucy discovered these facts and pub- 

 lished them the astonishment was great. Here 

 are some of his figures : — 



Fig. 10. 



But before long mathematicians hit upon a plan 

 by which they were able (or thought they were able) 

 to rob the figures of their startling character, and 



* See Marey, Animal Mechanism, p. 222, and Pettigrew, Animal 

 Locomotion, p. 133. 



C 2 



