25 



hatched later in the year than ordinary, and that 

 consequently they had not acquired sufficient 

 strength to undergo the fatigue of a long journey 

 upon the wing, at the time when the migration; of 

 the rest of their species took place. It is very pro- 

 bable that many of these, in order to shelter them- 

 selves from the 'inclemency of the weather, may, 

 provided with corresponding instincts, have retreated 

 to holes of rocks, and other recesses, where, from 

 cold and hunger, they may have sunk into a state of 

 torpidity *. Others, for the same reason, may hav^ 

 crept among the weeds, which grow by the sides of 

 rivers and ponds, where they may have been over- 

 whelmed by the increase of the water, occasioned 

 by the heavy rains which often happen towards the 

 end of autumn ; and some, which may not have been 

 long immersed, may probably have been restored to 



* See Montagu's Ornithological Dictionary, under the word 

 martin. 



It is by no means improbable that very cold and frosty 

 weather in spring may sometimes drive the swallow, just 

 arrived, into some snug retreat, where it may remain until the 

 warm weather returns. See Phil. Trans, vol. Ixv. p. 259 



