THE NATURAL HISTORY 



[LETT. 



for a week together at Spalding, without ever being told that 

 such a curiosity was just at hand. Pray tell me in your next 

 what sort of tree it is that contains such a quantity of herons' 

 nests ; and whether the heronry consists of a whole grove or 

 wood, or only of a few trees. 



It gave me satisfaction to find we accorded so well about the 

 c-aprimulgus : all I contended for was to prove that it often 

 chatters sitting as well as flying ; and therefore, the noise was 

 voluntary, and from organic impulse, and not from the resistance 

 of the air against the hollow of its mouth and throat. 



If ever 'I saw anything like actual migration, it was last 

 Michaelmas Day. I was travelling, and out early in the morn- 

 ing : at first there was a vast fog ; but by the time that I was 

 got seven or eight miles from home towards the coast, the sun 

 broke out into a delicate warm day. We were then on a large 

 heath or common, and I could discern, as the mist began to 

 break away, great numbers of swallows (Hirundines rusticce) 

 clustering on the stunted shrubs and bushes, as if they had 

 roosted there all night. As soon as the air became clear and 

 pleasant they all were on the wing at once ; and, by a placid 

 and easy flight, proceeded on southward towards the sea : after 

 this I did not see any more flocks, only now and then a 

 straggler. 



I cannot agree with those persons who assert that the swal- 

 low kind disappear gradually, as they come, for the bulk of 

 them seem to withdraw at once : only some few stragglers stay 

 behind a long while, and never, there is reason to believe, leave 

 this island. Swallows seem to lay themselves up, and to come 

 forth in a warm day, as bats do continually of a warm evening 

 after they have disappeared for weeks. For a very respectable 

 gentleman assured me that, as he was walking with some friends 

 under Merton wall on a remarkably hot noon, either in the last 

 week in December or the first week in January, he espied three 

 or four swallows huddled together on the moulding of one of 

 the windows of that college. I have frequently remarked that 

 swallows are seen later at Oxford than elsewhere : is this owing 

 to the vast massy buildings of that place, to the many waters 

 round it, or to what else ? 



