148 THE NATURAL HISTORY [LETT. 



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, with tender assiduity, 

 carry out what comes away from their young. Were it not for 

 this affectionate cleanliness the nestlings would soon be burnt 

 up, and destroyed in so deep and hollow a nest, by their own 

 caustic excrement. In the quadruped creation the same neat 

 precaution is made use of; particularly among dogs and cats, 

 where the dams lick away what proceeds from their young. 

 But in birds there seems to be a particular provision, that the 

 dung of nestlings is enveloped in a tough kind of jelly, and 

 therefore is the easier conveyed off without soiling or daubing. 

 Yet, as Nature is cleanly in all her ways, the young perform 

 this office for themselves in a little time by thrusting their tails 

 out at the aperture of their nest. As the young of small birds 

 presently arrive at their ijXt/a'a, or full growth, they soon become 

 impatient of confinement, and sit all day with their heads out 

 of the orifice, where the dams, by clinging to the nest, supply 

 them with food from morning to night. For a time the young 

 are fed on the wing by their parents ; but the feat is done by 

 so quick and almost imperceptible a slight, that a person must 

 have attended very exactly to their motions before he would be 

 able to perceive it. As soon as the young are able to shift for 

 themselves, the darns immediately turn their thoughts to the 

 business of a second brood, while the first flight, shaken off 



