OF SELBORNE 231 



LETTER LVI 



TO THE HONOURABLE DAINES HARRINGTON 



They who write on natural history cannot 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. Philo- 

 sophers 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 circumstances 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 architect. 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 oval, or com- 

 pressed. 



In the following instances instinct is perfectly uniform 

 and consistent. There are three creatures, the squirrel, 

 the field-mouse, and the bird called the nut-hatch {sitta 



