SWIMMING BIRDS. 269 



cliff, and skims the wide ocean for its food, only lays a single 

 egg ; and yet, the fulmar is, perhaps, the most numerous of 

 birds. 



All the birds of this order can swim, and with many of 

 them swimming is the principal motion ; but there are many 

 of them that fly more than they swim ; and others which 

 walk freely, rapidly, and gracefully. Their food is on the 

 surface, in the volume of the clear water, at the bottom in 

 the ooze, and along the beach, and in whichsoever of those 

 places it is to be found, or of whatsoever it consists, their 

 organization adapts them for procuring it in the easiest and 

 most successful manner. 



The under part of all of them is differently constructed 

 from that of land birds. The breast bone and ribs extend 

 along the whole of that part which is in the water; and 

 thus, that part of them does not move in the act of breath- 

 ing, but remains perfectly steady, and of the same shape. If 

 the under part were moveable during that operation, the 

 expansion would be impeded by the weight of the body, 

 which would have to be raised at every inspiration ; and the 

 feathers would be opened by the distension of the skin ; 

 therefore, they would breathe with difficulty, and the water 

 would penetrate the feathers. They are thus ribbed as the 

 lower part of a ship is, and any change which the form of 

 their bodies undergoes while they are swimming, takes place 

 in the portion which is out of the water. 



But though the under parts of all of them may thus be 

 compared to the hulls of vessels, they are not all of the same 

 form. They are fashioned to the kind of motion that they 

 are to have in the water, and also to that in the air, or on 

 the land. If the principal action be to remain floating and 

 dabbling, the lower part of the body is a punt ; if they are 

 to get rapidly through the air, the body is narrowed back- 

 wards, like that in the swift- winged land birds ; and if they 



