^ On Hybernation, 



equal to seventj-five miles an hour." — Edinb, Encyc, VoL 

 X. part 2nd, p. 737. 



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, 



" I have sometimes seen them as early as April the Sd, 

 when the mercury in the thermometer has been below 

 the freezing point. On the other hand, I have often taken 

 notice, that during a continuance of mild weather for the 

 space of a fortnight, in the month of April, not so much as 

 one swallow has appeared." — Foster on the Swallow, p. 13. 



Let 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. When animals become 

 torpid it is because their food is no longer to be procured, 

 and they arc 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. 



Sir Charles Mager, first Lord of the admiralty, relates 

 that on entering soundings in the British channel, a large 

 flock of swallows covered every rope of his vessel, and ap- 

 peared "spent and famished." Many instances of this 

 kind could be related if it were necessary, but those few 

 well attested facts are deemed sufficient to prove the act 

 of 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, 



