F. W. HEADLEY : WIND AND FLIGHT. 119 



There is no doubt that all large birds have much more 

 difficulty in rising than small ones have, and this is markedly 

 the case with big heavy sea-birds such as the Cormorant and 

 the Gannet. Helmholtz attributed this to the fact that 

 if the size of a bird is increased, the bulk (and con- 

 sequently the weight) must, according to mathematical 

 principles, increase more rapidly than the supporting 

 surface. Therefore, he argued, a really big flying bird is 

 an impossibility. This was before the day when Mr. 

 Maxim's flying machine, weighing over three tons, rose 

 buoyantly in the air. But, no doubt, big birds do rise 

 heavily, and they have an easily observable anatomical 

 peculiarity which partly accounts for it. When a lark 

 ascends, he gives his body a steep upward incline. If, then, 

 his wings are not simply to drive him backward, but are 

 to beat up and down, they must be capable of rotating 

 very freely at the shoulder joint. A pigeon also has much 

 freedom of rotation at this joint, as the accompanying 

 (h-awmg from a photograph shows. If, on the other hand. 



Fig. 3. — Pigeon Rising. (Drawn from a Photograph.) 



you take a live Cormorant or Gannet (or one that has just 

 been killed), you will find that it has very little power of 



