OF SELBORNE. 
i6i 
they even afFefl the clofe air of London. And I have not only feen 
them nefting in the Borough ^ but even in the Strand and Fleet-Jlreet ; 
but then it was obvious from the dinginefs of their afped that their 
feathers partook of the filth of that footy atmofphere. Martins 
are by far the leaft agile of the four fpecies ; their wings and tails 
are fhort, and therefore they are not capable of fuch furprifing 
turns and quick and glancing evolutions as the fwallow. Accord- 
ingly they make ufe of a placid eafy motion in a middle region of 
the air, feldom mounting to any great height, and never fweeping 
long together over the furface of the ground or water. They do 
not wander far for food, but affed fheltered diftrids, over fome 
lake, or under fome hanging wood, or in fome hollow vale, 
efpecially In windy weather. They breed the lateft of all the 
fwallow kind : in 1772 they had neftlings on to OBober the twenty- 
firft, and are never without unfledged young as late as Michaelmas. 
As the fummer declines the congregating flocks increafe in num- 
bers daily by the conftant acceflion of the fecond broods ; till at 
laft they fwarm in myriads upon myriads round the villages on the 
'Thames, darkening the face of the Iky as they frequent the aits 
of that river, where they rooft. They retire, the bulk of them I 
mean, in vafl: flocks together about the beginning of OElober : but 
have appeared of late years in a conflderable flight in this neighbour- 
hood, for one day or two, as late as November the third and fixth, 
after they were fuppofed to have been gone for more than a fort- 
night. They therefore withdraw with us the lateft of any fpecies. 
Unlefs thefe birds are very fhort-lived indeed, or unlefs they do not 
return to the diftrid where they are bred, they mufl undergo vaft 
devaftations fome how, and fome where ; for the birds that return 
yearly bear no manner of proportion to the birds that retire. 
Y 
Houfe- 
