STERNUM OF THE SWIFT. 335 



be a disadvantage to the falcon. She gives chace, 

 and such a momentum would throw her out when 

 her quarry doubles. Thus, though she always attempts 

 to gain and to keep the sky, she never rises to any 

 great height above her prey. 



The more produced sternum, and less perfectly 

 formed furcal bone of the eagle, show that her sternal 

 apparatus is not so exclusively, and therefore not so 

 powerfully, of a flying character. The enlargement 

 of the sternum backwards, and the greater strength 

 of the posterior angles, make it more of a carrying 

 basket, though it retains no small portion of the rapid 

 flight character. But strength rather than swiftness 

 is the character of the eagle's wing. The ordinary 

 flight is floating and hovering, and the wings are 

 more employed in bearing her up than in making 

 progressive motion. When she stoops it is always 

 from a height, and no inconsiderable portion of the 

 force with which she strikes arises from the momen- 

 tum of gravity acquired during the descent. This is 

 further proved by the fact that when the eagle misses 

 her stoop (which, from the goodness of her eye, and 

 the firmness of her body and wing, is not often) she 

 abandons, and takes the sky anew for fresh game ; 

 whereas when the falcon misses, she can continue 

 her flight and strike again. The falcon thus more 

 resembles the lightning from the cloud, which pro- 

 duces its effect by its own proper and inherent motion, 

 and the eagle more resembles the ball from a piece 

 of ordnance, which is urged onward by a force not 

 its own. 



In the sternum of the swift we have the maxi- 

 mum development of that bone as a carrying 

 basket in the air, but still accompanied with con- 

 siderable power of wing, though the swift never 



