are obvious. The first is, that though it may be dis-. 

 agreeable to swifts to remain beyond the beginning 

 of August, yet that they can subsist longer is unde- 

 niable. The second is, that this uncommon event, as 

 it was owing to the loss of the first brood, so it cor- 

 roborates my former remark, that swifts breed regu- 

 larly but once ; since, was the contrary the case, the 

 occurrence above could neither be new nor rare. 



P. S. — One swift was seen at Lyndon, in the 

 county of Rutland, in 1780, so late as the 3rd of 

 September. 



Selborne, Sept. 9, 1 78 1. 



LETTER XCVIL 

 To THE Honourable Daines Barrington. 



As I have sometimes known you make inquiries 

 about several kinds of insects, I shall here send you 

 an account of one sort which I little expected to 

 have found in this kingdom. I have often observed 

 that one particular part of a vine growing on the 

 walls of my house was covered in the autumn with 

 a black dust-like appearance, on which the flies fed 

 eagerly ; and that the shoots and leaves thus affected 

 did not thrive ; nor did the fruit ripen. To this sub- 

 stance I applied my glasses; but could not discover 

 that it had anything to do with animal life, as I at 



150 



