110 NATURAL HISTORY 



LETTER LVI. 



TO THE SAME. 



THEY who write on natural history can- 

 not too frequently advert to instinct, that 

 wonderful limited faculty, which, in some 

 instances, raises the brute creation as it 

 were above reason, and in others leaves 

 them so far below it. Philosophers have 

 defined instinct to be that secret influence 

 by which every species is impelled natu- 

 rally to pursue, at all times, the same way 

 or track, without any teaching or example; 

 whereas reason, without instruction, would 

 often vary and do that by many methods 

 which instinct effects by one alone. Now 

 this maxim must be taken in a qualified 

 sense; for there are instances in which 

 instinct does vary and conform to the cir- 

 cumstances of place and convenience. 



It has been remarked that every species 

 of bird has a mode of nidification peculiar 



