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strongly inclining it's tail against the wall, making that a fulcrum ; 

 and thus steadied it works and plasters the materials into the 

 face of the brick or stone. But then, that this work may not, 

 while it is soft and green, pull itself down by it's 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 it's 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 it's own, to eject the owner, and to 

 line it after it's 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 pro- 

 tuberances 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 inter- 

 woven 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. Was 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 into a tough kind of jelly, and therefore 

 is the easier conveyed off without soiling or daubing. Yet, as 

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