FEET OF AQUATIC BIRDS. 283 



and though the swimming- motion should be merely 

 a modification of the walking one, that is, by alternate 

 strokes of the two feet and never by both at once, 

 yet the articulation necessary for swimming is some- 

 what different from that which answers best for walk- 

 ing ; because the swimming feet must throw out a 

 little in order to clear the body, and this very throwing 

 out, which does not cause the body of the bird to 

 vibrate when it is supported by the water, does make 

 it vibrate when it is in the air. Sea birds as well as 

 sailors, may thus be known by the style of their 

 walking ; and though the causes be different, and the 

 o«e habit and the other structure, there is such a 

 resemblance between the rolling motion of the sea- 

 faring bird and the seafaring man, as alone would, to 

 careful observation, point them out as dwellers on the 

 same element. 



The web-fboted birds which may be considered as 

 the least aquatic, at least among the flat-billed divi- 

 sion, are the geese, especially such of them as, like 

 the domesticated goose, graze the meadows, or 

 otherwise find the greatest part of their food upon 

 land. These have most of the walking character in 

 their feet ; and when they swim they never use any 

 other than the walking motion, or that of paddling 

 alternately with the feet. 



But the body of the goose has a sort of boat, or 

 rather punt shape ; the sternum extends far back- 

 wards, and the tibise are so articulated that the tarsal 

 joints project much farther from the sides than they 

 do in land birds. Thus, though the axis of the body 

 is borne in a position nearly horizontal, the advance 

 of the foot, wide apart as the feet are from each 

 other, does not carry the centre of gravity directly 

 forward, but swings it round ; so that, unless when 



