THE EGG BIRDS 197 



and motionless. There was, in truth, hut little change in 

 their position, but it was maintained by constant adjustment 

 to the slight variations in the force and direction of the 

 wind. Wings were raised or lowered, widely spread or part- 

 ly closed; tails depressed or slightly elevated, and fan-like, 

 opened or shut. In short, there was a ceaseless if uncon- 

 scious effort on the part of the birds to maintain the bal- 

 ance between gravity acting in one direction, and air pres- 

 sure in another, and so well did they succeed that it was a 

 common sight to see one put its foot through its inner wing- 

 feathers and scratch its ear with as much ease as though it 

 had been on its nest. 



Sooty Tern Facing the Trade Wind 



Man, taking the Tern as a model, can duplicate its lines 

 and its area of wing expanse to weight, but who will endow 

 his creation of wood, and wire, and canvas with nerves, mus- 

 cles, and reflexes, which will enable it to encounter auto- 

 matically and with unfailing precision, the incomparably 

 unstable element in which it is designed to travel! 



The Bridled Terns were the least common of the three 

 species on the key in question; hut half a mile or more to the 

 south, on a newer key, several hundred were nesting. In gen- 

 eral habits they are like the Sooty Tern, but their nest-sites 

 are more commonly beneath a rock or in one of the innumer- 



