HOUSE-MARTIN. 183 



and green, pull itself down by its own weight, the 

 provident architect has prudence and forbearance 

 enough not to advance her work too fast ; but by 

 building only in the morning, and by dedicating 

 the rest of the day to food and amusement, gives 

 it sufficient time to dry and harden. About half 

 an inch seems to be a sufficient layer for a day. 

 Thus careful workmen when they build mud-walls 

 (informed at first perhaps by this little bird) raise 

 but a moderate layer at a time, and then desist ; 

 lest the work should become top-heavy, and so be 

 ruined by its own weight. By this method, in 

 about ten or twelve days, is formed an hemispheric 

 nest, with a small aperture towards the top, strong, 

 compact, and warm; and perfectly fitted for all 

 the purposes for which it was intended. But then 

 nothing is more common than for the house- 

 sparrow, as soon as the shell is finished, to seize 

 on it as its own, to eject the owner, and to line it 

 after its own manner. 



After so much labour is bestowed in erecting a 

 mansion, as nature seldom works in vain, martins 

 will breed on for several years together in the same 

 nest, where it happens to be well sheltered and 

 secure from the injuries of weather. The shell or 

 crust of the nest is a sort of rustic-work, full of 

 knobs and protuberances on the outside ; nor is 

 the inside of those that I have examined smoothed 

 with any exactness at all ; but is rendered soft and 

 warm, and fit for incubation, by a lining of small 

 straws, grasses, and feathers ; and sometimes by a 

 bed of moss interwoven with wool. In this nest 

 they tread, or engender, frequently during the 

 time of building ; and the hen lays from three to 

 five white eggs. 



At first, when the young are hatched, and are in 

 a naked and helpless condition, the parent birds, 



