74 NATURAL HISTORY OF SELBORNE. 
lived a great while, and seemed to enjoy themselves very well^ 
but never bred. Whether this circumstance will prove any thing 
either way I shall not pretend to say.* 
I return you thanks for your account of Cressi-hall ; but re- 
collect, not without regret, that in June 1746 I was visiting for 
a week together at Spalding, without ever being told that such 
a curiosity was just at hand. Pray send me word 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 
caprimulgus : all I contended for was to prove that it often chat- 
ters sitting as well as flying ; and therefore the noise was volun- 
tary, and from organic impulse, and not from the resistance of 
the air against the hollow of its mouth and throat. 
If ever I saw any thing like actual migration, it was last 
Michaelmas-day. I was traveUing, 
and out early in the morning : 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 swallow 
kind disappear some and some gradually, as they come, for the 
bulk of them seem to withdraw at once : only some stragglers 
stay behind a long v^hile, and do never, there is the greatest rea- 
son to believe, leave this island. Swallows seem to lay them- 
selves 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 walkmg 
with some friends under Merton-wall on a remarkably hot noon, 
either in the last week in December or the first week in January, 
* They are the same. — Ed. 
