STUDY OF NATURAL HISTORY 87 



common hen, I know, when the fury of incubation is on her, 

 will sit on a single shapeless stone, instead of a nest full of 

 eggs that have been withdrawn ; and, moreover, a hen turkey, 

 in the same circumstances, would sit on, in the empty nest, 

 till she perished with hunger. 



I think the matter might easily be determined whether a 

 cuckoo lays one or two eggs, or more, in a season, by opening 

 a female during the laying time. If more than one were come 

 down out of the ovary, and advanced to a good size, doubtless 

 then she would that spring lay more than one.* 



I will endeavour to get a hen, and examine. 



Your supposition, that there may be some natural obstruction 

 in singing birds while they are rnute, and that, when this is 

 removed, the song recommences, is new and bold. I wish you 

 could discover some good grounds for this suspicion. 



I was glad you were pleased with my specimen of the 

 caprimulgus, or fern-owl; you were, I find, acquainted with 

 the bird before. 



When we meet, I shall be glad to have some conversation 

 with you concerning the proposal you make of my drawing 

 up an account of the animals in 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, unsupported 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 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 

 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. 



* The fact we have recorded in our note, at page 81, shews that they 

 produce more than one egg ; and, if we may reason from analogy, it may 

 be mentioned that the yellow-billed cuckoo of America lays three or four 

 eggs, and the black-billed cuckoo of the same country lays from four to 

 five eggs ; and these birds are very closely allied in physical structure to 

 the common cuckoo. En. 



