PALMIPEDES. 361 



web ; and are placed behind the centre of gravity 

 when the body is horizontal. Hence, though their 

 use as walking organs is much diminished, their 

 power as oars is proportionally increased, and, conse- 

 quently, the birds move with great velocity both 

 upon and through the water ; in other words, they 

 swim and dive well. The plumage is peculiarly 

 thick, soft, and close, constituting an almost imper- 

 vious protection against the chilling influence of the 

 element on which they live. They are the only 

 birds in which the length of the neck exceeds that of 

 the feet ; a necessary provision, to enable many of 

 them to obtain their food at the bottom while swim- 

 ming on the surface. Their flesh has a remarkable 

 tendency to produce oily fat, another point in which 

 we trace an analogy with the Cetacea. The wings 

 vary much ; while in some they vie with the longest 

 and most powerful of the whole Class ; in others they 

 have dwindled down to mere fins, utterly useless as 

 organs of flight. Their food consists almost exclu- 

 sively of fish ; but a few of those whose range is con- 

 fined either to the fresh waters, or the vicinity of the 

 shore, feed also on mollusca and insects, and occa- 

 sionally on vegetable matters. 



Cuvier arranges the Swimming Birds into four 

 families, as follows : 



VOL. I. 



