194 SAND-MARTINS. 



occurs of their 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 tere- 

 brates 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, con- 

 sisting of fine grasses and feathers, usually goose fea- 

 thers, very inartificially laid together. 



Perseverance will accomplish any thing : 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 disabling herself; yet, with these 

 feeble instruments, have I seen a pair of them make 

 great dispatch, 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 dif- 

 ferent 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 



