ather be fine,
the martin begins to think in earnest of providing a mansion for its
family. The crust or shell of this nest seems to be formed of such dirt
or loam as comes most readily to hand, and is tempered and wrought
together with little bits of broken straws to render it tough and
tenacious. As this bird often builds against a perpendicular wall
without any projecting ledge under, it requires its utmost efforts to get
the first foundation firmly fixed, so that it may safely carry the
superstructure. On this occasion the bird not only clings with its
claws, but partly supports itself by strongly inclining its 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 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 a 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