264 
THE NATURAL HISTORY 
[LETT. 
way they become whimsical and unnatural, and liable to the 
objection due to him " who loves to vary every single thing 
prodigiously " — • 
" Qui variare ciipit rem prodigialiter unaiii." 
(HoR. Ars. Pod. 29.) 
LETTEE XCIX. 
TO THE HONOURABLE DAINES BARRINGTON. 
I THINK 1 have observed before, that much the most consider- 
able part of the house-martins withdraw from hence about the 
first week in October ; but that some, the latter broods I am 
now convinced, linger on till towards the middle of that month : 
and that at times, once perhaps in two or three years, a flight, 
for one day only, has shown itself in the first week in 
November. 
Having taken notice, in October 1780, that the last flight was 
numerous, amounting perhaps to one hundred and fifty, and 
that the season was soft and still, I was resolved to pay uncom- 
mon attention to those late birds : to find, if possible, where 
they roosted, and to determine the precise time of their retreat. 
The mode of life of these latter hirundines is very favourable to 
such a design ; for they spend the whole day in the sheltered 
district between me and the Hanger, sailing about in a placid, 
easy manner, and feasting on those insects which love to haunt 
a spot so secure from ruffling winds. As my principal object 
was to discover the place of their roosting, I took care to wait 
on them before they retired to rest, and was much pleaded to find 
that, for several evenings together, just at a quarter-past five in 
the afternoon, they all scudded away in great haste towards the 
south-east, and darted down among the low shrubs above the 
cottages at the end of the hill. This spot in many respects 
seems to be well calculated for their winter residence : for in 
many parts it is as steep as tlie roof of any house, and therefore 
