204 



ANIMAL LOCOMOTION. 



fall previous to alighting (fig. 107, below). Birds which 

 fish on the wing, as the osprey and gannet, precipitate 

 themselves from incredible heights, and drop into the water 

 with the velocity of a meteorite — the momentum which 

 they acquire during their descent materially aiding them 

 in their subaqueous flight. They emerge from the water 

 and are again upon the wing before the eddies occasioned 

 by their precipitous descent have well subsided, in some cases 

 rising apparently without effort, and in others running along 

 and beating the surface of the water for a brief period with 

 their pinions and feet. 



The Flight of Birds refer able to Muscular Exertion and Weight. 

 — The various movements involved in ascending, descending, 



Fig. 107.— The Red-headed Pochard (FuUgula ferina, Linn.) in the act of drop- 

 ping upon the water ; the head and body being inclined upwards and for- 

 wards, the feet expanded, and the wings dehvering vigorous short strokes 

 in a downward and forward direction. — Original. 



wheeling, gliding, and progressing horizontally, are all the 

 result of muscular power and weight, properly directed and 

 acting upon appropriate surfaces — that apparent buoyancy i^ 

 birds which we so highly esteem, arising not from superior- 

 lightness, but from their possessing that degree of solidity 

 which enables them to subjugate the air, — weight and inde- 

 pendent motion, i.e. motion associated with animal life, or 

 what is equivalent thereto, being the two things indispensable 

 in successful aerial progression. The weight in insects and 

 birds is in great measure owing to their greatly developed 

 muscular system, this being in that delicate state of tonicity 



