204 NATURAL HISTORY 



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 Novem- 

 ber, 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 

 enterprize of moment at all agitated their spirits. And this 

 was the case in the beginning of this very month; for, on 

 the fourth of November, more than twenty house-martins, 

 which, in appearance, had all departed about the seventh of 

 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 fourth was dark and mild, 

 and soft, the wind at south-west, and the thermometer at 

 58 X -^ ; a pitch not common at that season of the year. More- 

 over, it may not be amiss to add in this place, that whenever 

 the thermometer is above 50 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 this 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 Africa to enjoy, in March, the transient 

 summer of a couple of days. 



I am, &c. 



* [I have seen the Pipistrelle, the commonest of our bats, flying in 

 every month in the year j and whenever gnats are tempted to come forth, 

 the bat is sure to follow for a meal. T. B.j 



