212 THE NATURAL HISTORY [LETT. 



into the ground, and the swallows were seen no more until the 

 10th of April, when the rigour of the spring abating, a softer 

 season began to prevail. 



Again, it appears by my journals for many years past, that 

 house-martins retire, to a bird, about the beginning of October ; 

 so that a person 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 November, and often on 

 the fourth day of that month only for oue day ; and that not as 

 if they were in actual migration, but playing about at their 

 leisure and feeding calmly, as if no enterprise of moment at all 

 agitated their spirits. And this was the case in the beginning 

 of this very month ; for, on the 4th of November, more than 

 twenty house-martins, which, in appearance, had all departed 

 about the 7th 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 4th was 

 dark and mild, and soft, the wind at south-west, and the ther- 

 mometer at 58J; a pitch not common at that season of the 

 year. Moreover, 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. 



SELBORXE, Nov. 22, 1777. 



