t 2 39 ] 



But this is not all, as if I can depend upon my own obferva- 

 tions, as well as thofe of others, fwallows mould, according to 

 this fuppofition, always firft appear in flocks on the Southern coaft 

 of this ifiand ; whereas they are feen but in fmall numbers, dif- 

 perfed almoft equally over all parts of it, and if any cold weather 

 happens they then immediately difappear, being obferved in the 

 fame numbers again when the mild weather is more confirmed, 

 and are afterwards joined by myriads from every lurking place 

 and retreat. 



All animals are endowed with a providential inftinct to avoid 

 what may be. prejudicial to them, and therefore it mould feem 

 that the fwallow tribe would never leave the coaft of Africa in 

 their fpring migration to the Northward till a month later than 

 they generally appear, as then there would be no occafion for a 

 fudden retreat on the frofls, which are fo frequently experienced 

 in the early parts of our fpring. Lying however in their torpid 

 ftate they cannot refill the mild influence of the firft genial 

 weather, but know where to fecure themfelves when it becomes 

 fevere. 



That the fwallow- tribe are concealed during the winter, not 

 far from the place where they have been hatched, may be inferred 

 from the following facts. 



Mr. Stephens, F. S. A. hath informed me that martins con- 

 tinued to have a neft for 16 years together in the hall of an old 

 houfe which belongs to him at Camerton in Somerfetmire, 

 though the door was conftantly fhut during the night, and iomc- 

 rimes for a few hours during day-light, when the parent birds 

 muft have been not a little impatient to feed their neftlings. 



The fame fact hath been attefted to me by Mr. Sanxay,. with 

 regard to the porch of a gentleman's houfe in Derbyshire b , though 



b John Burrows,. Efq. of Overdone, near Derby. 



- the. 



