NATURAL HISTORY OF SELBORNE. 261 



LETTER LVI. 



TO THE SAME. 



THEY who write on natural history cannot too frequently advert 

 to instinct, that wonderful limited faculty, which, in some instances, 

 rises 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 naturally 

 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 circum- 

 stances of place and convenience. 



It has been remarked that every species of bird has a mode of 

 nidification peculiar to itself, so that a school-boy would at once 

 pronounce on the sort of nest before him. This is the case among 

 fields and woods, and wilds ; but, in the villages round London, 

 where mosses and gossamer, and cotton from vegetables, are hardly 

 to be found, the nest of the chaffinch has not that elegant finished 

 appearance, nor is it so beautifully studded with lichens, as in a 

 more rural district ; and the wren is obliged to construct its house 

 with straws and dry grasses, which do not give it that rotundity 

 and compactness so remarkable in the edifices of that little archi- 

 tect. Again, the regular nest of the house-martin is hemispheric ; 

 but where a rafter, or a joist, or a cornice, may happen to stand in 

 the way, the nest is so contrived as to conform to the Obstruction, 

 and becomes flat, or compressed. 



In the following instances instinct is perfectly uniform and con- 

 sistent. There are three creatures, the squirrel, the field-mouse, 

 and the bird called the nut-hatch (sit fa Europced), which live much 

 on hazel-nut ; and yet they open them each in a different way. 

 The first, after rasping off the small end, splits the shell in two 

 with his long fore-teeth, as a man does with his knife ; the second 

 nibbles a hole with his teeth, so regular as if drilled with a wimble, 



