104 ADAPTATION OF NATURAL SITUATIONS. 



or dislocatedjoints, the possible, and indeed the very 

 likely consequences. Thus we see that in nature's 

 mechanics, the contrivances by which purposes are 

 accomplished, are not only the best adapted for those 

 purposes, but they are applied for the accomplish- 

 ment of them in the best manner, both for success in 

 the end and for safety to the instrument. 



This principle is one of the most difficult to carry 

 into complete, or even tolerable effect, in the whole 

 compass of human mechanics; but it is one which nature 

 invariably displays in all her structures, and in all 

 the varieties of their working. This must, however, 

 in the case of animals, and especially in that of pre- 

 datory animals, be considered true only as affects the 

 animal to which the structure belongs : for as the 

 prey and the preyer are part of the general system of 

 nature, and as such made for each other, the perfec- 

 tion of the system requires that the prey should be 

 taken as much at a disadvantage to itself as there is 

 advantage on the part of the preyer. 



And this is well exemplified in all birds which 

 strike, or otherwise capture their prey on the wiiit:, 

 and more especially in the jer-falcon, which may be 

 said to perform that operation in most magnificent 

 style, at least in so far as the slaughter of one bird by 

 another can be considered magnificent. The jer- 

 falcon, at forward flight, and without the excitement 

 produced by the joint effects of hunger and the sight 

 of that which can appease it, can cleave the air at the 

 rate of at least one hundred miles in the hour ; but 

 when she works herself to the top of her bent, and 

 then rushes forward in the tempest of her impetuosity. 

 her motion is double, triple, nay, probably more than 

 five, or even ten times that rate ; so that if she could 

 hold on with the same speed, she would keep pace 



