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 :— 
Surface per 1lb. weight. 
ins 
Bq. yds. ft. , 
Gnat 2 ia Bade: | 6 105 
Butterfly .. 3 8 87 
Swallow .. Bn, | 4 18 
Piecon |... fy eae 1 14 
Stork 0 0 132* 
Fic. 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. 
G.2 
