96 NATURAL HISTORY 



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

 the county of Rutland, in 1782, so late as 

 the third of September. 



LETTER LIII. 



TO THE SAME. 



As I have sometimes known you make in- 

 quiries 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 had 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 

 substance I applied my glasses ; but could 

 not discover that it had any thing to do 

 with animal life, as I at first expected : 



