RAVENS, CURLEWS, AND EIDER-DUCKS 151 



and with a kick up, as it were, of the legs and tail. 

 If one sits on a height and they come sufficiently 

 near inshore to look down on them at an acute 

 angle, one can follow their course under the water, 

 often for a -considerable time. One remarks then 

 that the wings are moved both together — flapped or 

 beaten — so that the bird really flies through the water. 

 In flight, however, they are spread straight out with- 

 out a bend in them, whereas here they are all the 

 while flexed at the joint, being raised from and 

 brought downwards again towards the sides in the 

 same position in which they repose against them 

 when closed. These birds — and, no doubt, the other 

 divers — dive not only to catch fish, but also for the 

 sake of speed. I have seen them when travelling 

 steadily along the shore duck down and swim or 

 fly like this, in a straight line and but just below the 

 surface of the water, always pursuing the same direc- 

 tion, and seeming to have no difficulty in guiding them- 

 selves. The speed was very much greater than when 

 they merely paddled on the surface. Thus we may 

 see, perhaps, how such birds as the great auk and the 

 penguins came to lose the power of flight. They could 

 fly in two ways, either through the air or the water. 

 The first — as long as they retained it at all, probably — 

 was much the quicker ; but the other was quick enough 

 for their purposes, and the effort required to rise from 

 the water was thus dispensed with. These razorbills 

 dived in order to g€t more quickly to some point for 

 which they were making. They might have got there 

 still sooner by flying, but the time saved was evidently 

 not worth that effort to them. But the power of flight 

 might be long retained by a bird — though useless to it 



