156 NATURAL HISTOEY 



considerable flight in this neighbourhood, for one day or two, 

 as late as November the third and sixth, after they were 

 supposed to have been gone for more than a fortnight. They 

 therefore withdraw with us the latest of any species. Unless 

 these birds are very short-lived indeed, or unless they do not 

 return to the district where they are bred, they must undergo 

 vast devastations some how, and some where ; for the birds 

 that return yearly bear no manner of proportion to the birds 

 that retire. 



House-martins are distinguished from their congeners by 

 having their legs covered with soft downy feathers down to 

 their toes. They are no songsters ; but twitter in a pretty 

 inward soft manner in their nests. During the time of 

 breeding they are often greatly molested with fleas. 



I am, &c. 



LETTER XVII. 



TO THE SAME. 



Kingmer, near Lewes, Dec. 9, 1773. 

 DEAR SIR, 



I RECEIVED your last favour just as I was setting out for this 

 place ; and am pleased to find that my monography met with 

 your approbation. My remarks are the result of many years 

 observation ; and are, I trust, true in the whole : though I do 

 not pretend to say that they are perfectly void of mistake, or 

 that a more nice observer might not make many additions, 

 since subjects of this kind are inexhaustible. 



If you think my letter worthy the notice of your respect- 

 able society, you are at liberty to lay it before them; and 

 they will consider it, I hope, as it was intended, as an humble 

 attempt to promote a more minute inquiry into natural 

 history ; into the life and conversation of animals. Perhaps 

 hereafter I may be induced to take the house-swallow under 

 consideration; and from that proceed to the rest of the 

 British hirundines. 



