102 
THE NATURAL HISTORY 
[LETT. 
When birds come to suffer by severe frost, I find that the 
first that fail and die are the redwing, fieldfares, and then the 
song-thrushes. 
You wonder, with good reason, that the hedge-sparrows, &c. 
can be induced at all to sit on the egg of the cuckoo without 
being scandalized at the vastly disproportioned size of the sup- 
posititious egg; but the brute creation, I suppose, have very 
little idea of size, colour, or number. For the common hen, as 
1 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been withdrawn : and, moreover, a hen- turkey, jn the same cir- 
cumstances, 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 was come 
down out of the ovary, and advanced to a good size, doubtless 
then she would that spring lay more than one. I will endea- 
vour to get a hen, and examine her. 
Your supposition that there may be some natural obstruction 
in singing birds while they are mute, 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 capri- 
midgits, 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 par- 
tiality 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. 
