$2 On Hybernation. 
equal to seventy-five miles an hour.’’—Edinb. Encyc. Vol. 
. part 2nd, p. 737. ee 
If we calculate the flight of the swallow to be equally 
rapid as that of the falcon, the bird that this morning bade 
adieu to its summer nest within our barns, might in two 
days rest his weary wings beyond the isthmus of Panama. 
If the swallow emerged in the spring from a watery bed, 
its resuscitation would be governed by the thermometer; 
but this is not the case. Foster says, 
_*] have sometimes seen them as early as April the 2d, 
when the mercury in the thermometer has heii belo 
the freezing point. On the other hand, I have often taken 
notice, that during a continuance of mild weather for 
space of a fortnight, in the month of April, not so much as 
one swallow has appeared.” — Foster on the Swallow. p. 13. 
t us now examine why this bird should not hybernate 
as it has been repeatedly asserted to do. If we try its 
specific gravity we shall find it requires some weight to 
_ Sink it in water. It disappears too at a time so early that 
it is impossible the cold could produce torpidity, and we 
cannot suppose it to be voluntary. Whenani om 
oO 
rpid it is because their food is no longer to be procured, 
and they are so by necessity; but it is not the same with 
the swallow. It loves the soft breezes of the south, and 
almost the first north wind reminds it of its equinoctial 
haunts. 
Adanson, in his voyage to Senegal, states that four 
swallows alighted on his vessel in October, when fifty 
leagues from the coast of the latter place; and that they 
winter in Senegal, where they roost on the sand of the 
shore, and never build in that country. 
well attested facts are deemed sufficient to prove the act 
migration. 
With regard to the point of their migration it may be 
safely concluded to be so far south on both continents as 
not to be touched by the cold. Capt. Henderson, of the 
British army, relates that he saw myriads in Honduras, 
