148 RETURN OF BIRDS. 



you make of my drawing up an account of the 

 animals of this neighbourhood. Your partiality 

 towards my small abilities persuades you, I fear, 

 that I am able to do more than is in my power ; 

 for it is no small undertaking for a man unsup- 

 ported and alone to begin a natural history from 

 his own autopsia ! Though there is endless room 

 for observation in the field of nature, which is 

 boundless, yet investigation (where a man endea- 

 vours to be sure of his facts) can make but slow 

 progress ; and all that one could collect in many 

 years would go into a very narrow compass. 



Some extracts from your ingenious " Investi- 

 gations of the difference between the present 

 temperature of the air in Italy," &c. have fallen 

 in my way, and gave me great satisfaction. They 

 have removed the objection that always arose in 

 my mind whenever I came to the passages which 

 you quote. Surely the judicious Virgil, when 

 writing a didactic poem for the region of Italy, 

 could never think of describing freezing rivers, 

 unless such severity of weather pretty frequently 

 occurred ! 



P.S. Swallows appear amidst snows and frost. 



VI. 



THE severity and turbulence of last month 

 [April] so interrupted the regular process of 

 summer migration, that some of the birds do but 

 just begin to show themselves, and others are 

 apparently thinner than usual ; as the white-throat, 

 the black-cap, the red-start, the fly-catcher. I 

 well remember, that after the very severe spring, 

 in the year 1739-40, summer birds of passage 

 were very scarce. They come probably hither 



