150 THE NATURAL HISTORY [LETT. 



east and south-west) are too shallow, the nests are washed down 

 every hard rain ; and yet these birds drudge on to no purpose from 

 summer to summer, without changing their aspect or house. It 

 is a piteous sight to see them labouring when half their nest is 

 washed away, and bringing dirt " to patch the ruins of a fallen 

 race " " generis lapsi sarcire ruinas." Thus is instinct a most 

 wonderful but 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 arid 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 atinoshhere. 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 the 

 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 neighbourhood, 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 fortnight. 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 



