NATURAL HISTORY OF SELBORNE 71 



abounding but near vast pools or rivers ; and in particular 

 it has been remarked that they swarm in the banks of the 

 Thames in some places below London-bridge. 



It is curious to observe with what different degrees of 

 architectonic skill Providence has endowed birds of the 

 same genus, and so nearly correspondent in their general 

 mode of life ! for while the swallow and the house-martin 

 discover the greatest address in raising and securely fixing 

 crusts or shells of loam as cunabula for their young, the 

 bank-martin terebrates a round and regular hole in the 

 sand or earth, which is serpentine, horizontal, and about 

 two feet deep. At the inner end of this burrow does 

 this bird deposit, in a good degree of safety, her rude 

 nest, consisting of fine grasses and feathers, usually goose- 

 feathers, very inartificially laid together. 



Perseverance will accomplish anything ; though at first 

 one would be disinclined to believe that this weak bird, 

 with her soft and tender bill and claws, should ever be 

 able to bore the stubborn sand-bank without entirely dis- 

 abling herself ; yet with these feeble instruments have I 

 seen a pair of them make great despatch, and could remark 

 how much they had scooped that day by the fresh sand 

 which ran down the bank, and was of a different colour 

 from that which lay loose and bleached in the sun. 



In what space of time these little artists are able to 

 mine and finish these cavities I have never been able to 

 discover, for reasons given above ; but it would be a matter 

 worthy of observation, where it falls in the way of any 

 naturalist to make his remarks. This I have often taken 

 notice of, that several holes of different depths are left 

 unfinished at the end of summer. To imagine that these 

 beginnings were intentionally made in order to be in the 

 greater forwardness for next spring is allowing perhaps too 

 much foresight and rerum prudentia to a simple bird. May 

 not the cause of these latebrce being left unfinished arise from 

 their meeting in those places with strata; too harsh, hard, 

 and solid for their purpose, which they relinquish, and 

 go to a fresh spot that works more freely ? Or may they 



