160 NATURAL HISTORY OF SELBORNE. 
sight to see them labouring when half their nest is washed away and 
bringing dirt... . “‘ generis lapsi sarcire ruinas.” Thus is instinct 
a most wonderful unequal faculty ; in some instances so much above 
reason, in other respects so far below it! Martins love to frequent 
towns, especially if there are great lakes and rivers at hand; nay 
they even affect the close air of London. And I have not only seen 
them nesting in the Borough, but even in the Strand and Fleet 
Street ; but then it was obvious from the dinginess of their aspect 
that their feathers partook of the filth of that sooty atmosphere. 
Martins are by far the least agile of the four species ; their wings and 
tails are short, and therefore they are not capable of such surprising 
turns and quick and glancing evolutions as the swallow. Accord- 
ingly they make use of a placid easy motion in a middle region of 
the air, seldom mounting to any great height, and never sweeping 
long together over the surface of the ground or water. They do 
not wander far for food, but affect sheltered districts, over some 
lake, or under some hanging wood, or in some hollow vale, espe- 
cially in windy weather. They breed the latest of all the swallow 
kind: in 1772 they had been nestlings on to October 2Ist, and are 
never without unfledged young as late as Michaelmas. 
As the summer declines the congregating flocks increase in 
numbers daily by the constant accession of the second broods ; till 
at last they swarm in myriads upon myriads round the villages on 
the Thames, darkening the face of the sky as they frequent the aits 
of that river, where they roost. They retire, the bulk of them I 
mean, in vast flocks together about the beginning of October; but 
have appeared of late years ina considerable flight in this neigh- 
bourhood, for one day or two, as late as November the 3rd and 6th, 
after they were supposed to have been gone for more than a fort- 
night. They therefore withdraw with us the latest of any species. 
Unless these birds are very short-lived indeed, or unless they do not 
return to the district where they are bred, they must undergo vast 
devastations somehow, and somewhere; for the birds that return 
yearly bear no manner of proportion to the birds that retire. 
House-martins are distinguished from their congeners by having 
their legs covered with soft downy feathers down to their toes.* 
They are no songsters ; but twitter in a pretty inward soft manner 
in their nests. During the time of breeding they are often greatly 
molested with fleas. I am, &c. 
* And a separate genus has been made for it in consequence, which is adopted by some 
crnithclogists. 
