1 30 NA TURAL HIS TOR Y OF SELB ORNE. 



autopsia ! Though there is endless room for observation in the 

 field of nature, which is boundless, yet investigation (where a man 

 endeavours 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 " Investigations of the Dif- 

 ference between the Present Temperature of the Air in Italy," c., 

 have fallen in my way j and gave me great satisfaction : they have 

 removed the objections 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. 



