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 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," etc., have fallen
in my way, 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.