178 STUDY OF NATURAL HISTORY. 



increased. Thus, in America, the warblers are par- 

 ticularly numerous, and not only feed upon creeping 

 insects, but also upon those winged tribes which 

 frequent the foliage for shelter. The more we see 

 of the economy of animals, the more do we find 

 stratagem opposed to stratagem : so that modes of 

 defence or of self-preservation, which even the 

 reason of man would suppose perfectly effectual, 

 are still found to be unavailing, in all cases, against 

 the address of those enemies whose attacks are to 

 be dreaded. In the foregoing remarks, we have 

 been insensibly led to illustrate more than one of 

 the positions before touched upon. The student, 

 however, will thus perceive, to the full extent, the 

 indispensable necessity of observing and recording 

 every fact, even the most apparently trivial, con- 

 nected with the habits of animals. 



(120.) But, however attentively we may study 

 the manners of living animals, there must ever re- 

 main a large proportion whose economy has never 

 been recorded, and of which we can consequently 

 know nothing from actual observation. Here, then, 

 we must have recourse to analogical reasoning. It 

 is found that certain habits are always indicated by 

 a correspondence of structure. Among birds, for 

 instance, we observe that all those which live ha- 

 bitually upon the ground, like the partridge, the 

 turkey, and the domestic fowl, have strong, ele- 

 vated legs; while in birds which rest only upon 

 trees, like the swallow, these members are short and 

 weak. We know, from experience, the universality 

 of these facts ; and we thence conclude that all birds 

 so constructed, have corresponding habits, although 



