SELBORNE, _Nov._ 22_nd_, 1777.
Dear Sir,--You cannot but remember that the 26th and 27th of last March
were very hot days--so sultry that everybody complained and were restless
under those sensations to which they had not been reconciled by gradual
approaches.
This sudden summer-like heat was attended by many summer coincidences;
for on those two days the thermometer rose to 66 degrees in the shade;
many species of insects revived and came forth; some bees swarmed in this
neighbourhood; the old tortoise, near Lewes, in Sussex, awakened and came
forth out of its dormitory; and, what is most to my present purpose, many
house-swallows appeared and were very alert in many places, and
particularly at Chobham, in Surrey.
But as that short, warm period was succeeded as well as preceded by
harsh, severe weather, with frequent frosts and ice, and cutting winds,
the insects withdrew, the tortoise retired again into the ground, and the
swallows were seen no more until the 10th April, when, the rigour of the
spring abating, a softer season began to prevail.
Again, it appears by my journals for many years past that house-martins
retire, to a bird, about the beginning of October, so that a person not
very observant of such matters would conclude that they had taken their
last farewell; but then it may be seen in my diaries also that
considerable flocks have discovered themselves again in the first week of
November, and often on the fourth day of that month, only for one day,
and that not as if they were in actual migration, but playing about at
their leisure and feeding calmly, as if no enterprise of moment at all
agitated their spirits. And this was the case in the beginning of this
very month; for on the 4th November more than twenty house-martins,
which, in appearance, had all departed about the 7th October, were seen
again for that one morning only sporting between my fields and the
Hanger, and feasting on insects which swarmed in that sheltered district.
The preceding day was wet and blustering, but the 4th was dark, and mild,
and soft, the wind at south-west, and the thermometer at 58.5 degrees, a
pitch not common at that season of the year. Moreover, it may not be
amiss to add in this place, that whenever the thermometer is above 50
degrees, the bat comes flitting out in every autumnal and winter month.
From all these circumstances laid together, it is obvious that torpid
insects, reptiles, and quadrupeds, are awakened from their profoundest
slumbers by a little untimely warmth, and therefore that nothing so much
promotes its death-like stupor as a defect of heat. And farther, it is
reasonable to suppose that two whole species, or at least many
individuals of those two species of British hirundines, do never leave
this island at all, but partake of the same benumbed state; for we cannot
suppose, that after a month's absence, house-martins can return from
southern regions to appear for one morning in November, or that house-
swallows should leave the districts of Asia to enjoy in March the
transient summer of a couple of days.