kittens play together, is there not a tacit contract, that they will not
hurt each other? And does not your favorite dog expect you should give him
his daily food, for his services and attention to you? And thus barters his
love for your protection? In the same manner that all contracts are made
amongst men, that do not understand each others arbitrary language.

_Construction of their Nests._

1. They seem to be instructed how to build their nests from their
observation of that, in which they were educated, and from their knowledge
of those things, that are most agreeable to their touch in respect: to
warmth, cleanliness, and stability. They choose their situations from their
ideas of safety from their enemies, and of shelter from the weather. Nor is
the colour of their nests a circumstance unthought of; the finches, that
build in green hedges, cover their habitations with green moss; the swallow
or martin, that builds against rocks and houses, covers her's with clay,
whilst the lark chooses vegetable straw nearly of the colour of the ground
she inhabits: by this contrivance, they are all less liable to be
discovered by their adversaries.

2. Nor are the nests of the same species of birds constructed always of the
same materials, nor in the same form; which is another circumstance that
ascertains, that they are led by observation.

In the trees before Mr. Levet's house in Lichfield, there are annually
nests built by sparrows, a bird which usually builds under the tiles of
houses, or the thatch of barns. Not finding such convenient situations for
their nests, they build a covered nest bigger than a man's head, with an
opening like a mouth at the side, resembling that of a magpie, except that
it is built with straw and hay, and lined with feathers, and so nicely