NATURAL HISTORY OF SELBORNE 217 



I have only to add that were the bushes, which cover some 

 acres, and are not my own property, to be grubbed and care- 

 fully examined, probably those late broods, and perhaps the 

 whole aggregate body of the house-martins of this district, 

 might be found there, in different secret dormitories ; and that, 

 so far from withdrawing into warmer climes, it would appear 

 that they never depart three hundred yards from the village. 



LETTER LVI 



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. Philoso- 

 phers have defined instinct to be that secret influence by which 

 every species is compelled 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 in- 

 stances 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 beauti- 

 fully 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 compressed. 



