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THE NATURAL HISTORY OF SELBORNE, I4I 
on to no purpose from summer to summer, without changing 
their aspect or house. It is a piteous sight to see them labor- 
ing when half their nest is washed away, and bringing dirt “ to 
patch the ruins of a fallen house.” ‘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 there- 
fore they are not capable of such surprising turns and quick 
and glancing evolutions as the swallow. Accordingly 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, especially in windy weather. ‘They breed the latest of all 
the swallow kind: in 1772 they had nestlings on to October 
21st, 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 in a 
considerable flight in this neighborhood, for one day or two, 
as late as November 3d and 6th, after they were supposed to 
have been gone for more than a fortnight. ‘They therefore 
