e objection due to him.

"Qui variare cupit rem prodigialiter unam."

I am, etc.

LETTER LV.

_October_ 10_th_, 1781.

Dear Sir,--I think I have observed before that much of the most
considerable 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 uncommon attention to these 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 pleased 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,
seemed to be well calculated for their winter residence; for in many
parts it is as steep as the roof of any house, and therefore secure from
the annoyances of water; and it is moreover clothed with beechen shrubs,
which, being stunted and bitten by sheep, make the thickest covert
imaginable, and are so entangled as to be impervious to the smallest
spaniel; besides, it is the nature of underwood beech never to cast its
leaf all the winter, so that, with the leaves on the ground and those on
the twigs, no shelter can be more complete. I watched them on the 13th
and 14th October, and found their evening retreat was exact and uniform;
but after this they made no regular appearance. Now and then a straggler
was seen, and on the 22nd October, I observed two in the morning over the
village, and with them my remarks for the season ended.

From all these circumstances put together, it is more than probable that
t