288 FEET OF mVING BIRDS. 



the tarsi short, the tibiee rather lengthened, which 

 throws the joint of the tarsus backward ; the toes and 

 webs larger, and the hind toe with a little web. They 

 do not dive habitually ; for though they are less 

 fitted for dabbling than the others, they do practise 

 it a little, and they also feed along- the strands ; but 

 they often appear to get down for change of motion, 

 as well as for food ; and on such occasions they move 

 more quickly below the water than they can on the 

 surface. 



Of course when they are once down, and the water 

 hsis closed over them, there is no more paddling with 

 the alternate feet. That is properly a land motion, 

 and can be used as the sole means of progression 

 only when part, at least, of the body is in a rarer 

 medium than that against which the foot acts. Thus, 

 when the bird is under, it immediately brings all the 

 four extremities into action, in the same manner as is 

 done by frogs, water-tortoises, and all other animals 

 which have four extremities and swim immersed. 



This is the style in which man swims, and also 

 those mammalia which have not a trotting pace be- 

 tween the slow walk and the gallop, the common pig 

 for instance. It is also the style of all aquatic mam- 

 malia, and indeed of all vertebrated animals which 

 inhabit the waters ; for those which have no fins of 

 any sort cannot advance with one flexure of the body, 

 but must twine in two or more, eel-fashion, according 

 to their length. The golden-eye is the duck, visiting 

 the British shores, which has this action in greatest 

 perfection ; and the foUomng is the figure of its foot. 



But even in the birds last mentioned, progressive 

 motion under water is only an occasional action, and 

 therefore they have it not in the finest style. The 

 grebes which, notwithstanding their merely lobed 



