"It is easy to suppose that they may, like bats
and flies, have been awakened by the influence
of the sun, amidst their secret haunts, where
they have spent the uncomfortable foodless
months in a torpid state, and the profoundest of
slumbers." Still he speaks cautiously, for
immediately after he remarks: "That they can
retire to rest, and sleep away these uncomfortable
periods, as bats do, is a matter rather to be
suspected than proved." But the great Linnæus
himself lent his countenance to this fancy,
and it became in the last century a common
mode of expression among those who were
accustomed to derive their ideas from contemporary
authorities. Thus Sturm, in his Reflections
(April 28), says: "The mild air of spring
awakens the swallow from his benumbed state."

It is worthy of remark, however, that,
although numerous stories are recorded of torpid
birds being turned up from their winter retreats,
they are always, or nearly always, upon hearsay
evidence, and doubtless have lost nothing in
the transmission from one person to another.
There is scarce an instance of a person describing
such a circumstance from his own observation,
unless, indeed, it were "a great many years
ago, when he was a boy," and probably, therefore,
incapable of judging of the evidence before
him. White tells us two such tales—one of a
clergyman of an inquisitive turn, who assured him
that when he was a great boy, some workmen, in
pulling down the battlements of a church tower
early in spring, found two or three swifts among
the rubbish, which were, at first appearance,
dead, but, on being carried towards the fire,
revived. And another "intelligent person" (every
one is an intelligent person who has seen something
that no one else has seen) stated that while
he was a schoolboy at Brighton, a great fragment
of the chalk cliff fell down one stormy winter
on the beach, and that many people found
swallows among the rubbish; but, adds White,
"on my questioning him whether he saw any of
those birds himself, to my no small disappointment
he answered me in the negative, but that
others assured him they did." Although, therefore,
he leaned to the theory of hiding, he is
forced to confess that he never heard any such
account worth attending to. And with regard
to the other soft-billed and short-winged birds
of passage, against the possibility of whose
migration there seemed to be many difficulties,
he declares that, "as to their hiding, no man
pretends to have found any of them in a torpid
state in winter." He himself tested the truth of
the theory by digging out the nest of the sand-
martins from the holes in a bank, and satisfied
himself that they were entirely deserted.

Markwick, a contemporary of White, and who
was rather disposed to put faith in the hiding
of birds in winter, very candidly reviews the
circumstances which have led to that idea. In
very early spring, and sometimes immediately
after very cold, severe weather, on its growing
a little warmer, a few swallows suddenly make
their appearance long before the generality of
them are seen. These appearances, he observes,
certainly favour the opinion of their passing the
winter in a torpid state, but do not absolutely
prove the fact;  for who ever saw them reviving
of their own accord from their torpid state,
without being first brought to the fire, and, as
it were, forced into life again? Soon after which
revivification they constantly die. This is, indeed,
the key to any occasional cases of benumbed
birds which may possibly have been found early
in the season. Their condition is not a natural
and physiological one, but an unnatural and
dangerous one, produced by unwonted cold, from
which the probability is they cannot recover.

The real state of the case is, that migrating
birds are subject to certain evils arising from
their instinct, which are of two kinds—one
met with on their arrival in this country,
another likely to be encountered at the time of
their departure—one, that is, in early spring,
the other in late autumn. We cannot in the
present paper indicate the principle of migration
at any length; but it will be sufficient to
remark that the movements of birds being
regulated by the seasons, and proximately by the
heat of the sun, and both our climate and solar
heat being proverbially uncertain and liable to
variation, the delicate birds, which winter in a
warm climate, return to this country only to
encounter the unseasonable weather, cold, wet,
and it may be frost and snow, which occasionally
make their appearance even in April. To
such inclement weather they soon succumb, and,
retiring to their roosting-places, become
benumbed and thrown into a helpless condition,
which is only the precursor of their death; and
in that condition they may have been sometimes
found. Or it may even happen that they have
arrived in March, or much earlier than the
usual time, owing to an advanced season in the
country they have left, when the results would
be still more marked. Occasionally, the bad
weather being transitory, they may be little
seen for a few days after their first appearance,
when, fine and mild weather returning, they
recover themselves, and come out as usual.

With regard to the accidents of their autumnal
migration, they are of a more limited character,
and do not affect the species in the wholesale
manner of those just alluded to. That it
frequently happens that a bird has been seen long
after its companions have quitted their summer
residence, there can be no doubt. Such a
circumstance, indeed, is one of those exceptional
cases which prove the rule. Some defect of
flight may have prevented it from accompanying
the main body, recovering which, it would
make the attempt to follow them, for the
instinct is strong upon them at that season of the
year; but we may safely conclude that such a
bird, if it was forced to remain, would not be
able either to subsist or to exist through the
winter. The swallow produces two and even
more broods during the season, the second
brood being brought out about the middle or
end of August. But if the second brood be
retarded from any cause, or if a third brood be
hatched late in the season, the impulse of