by ten days or a fortnight. These industrious artificers are at
their labours in the long days before four in the morning. When they fix
their materials they plaster them on with their chins, moving their heads
with a quick vibratory motion. They dip and wash as they fly sometimes
in very hot weather, but not so frequently as swallows. It has been
observed that martins usually build to a north-east or north-west aspect,
that the heat of the sun may not crack and destroy their nests; but
instances are also remembered where they bred for many years in vast
abundance in a hot stifled inn-yard against a wall facing to the south.

Birds in general are wise in their choice of situation; but in this
neighbourhood every summer is seen a strong proof to the contrary at a
house without eaves in an exposed district, where some martins build year
by year in the corners of the windows. But, as the corners of these
windows (which face to the south-east and south-west) are too shallow,
the nests are washed down every hard rain; and yet these birds drudge on
to no purpose from summer to summer, without changing their aspect or
house. It is a piteous sight to see them labouring when half their nest
is washed away and bringing dirt . . . "_generis lapsi sarcire ruinas_."
Thus is instinct a most wonderful unequal faculty; in some instances so
much above reason, in other respects so far below it! Martins love to
frequent towns, especially if there are great lakes and rivers at hand;
nay, they even affect the close air of London. And I have not only seen
them nesting in the Borough, but even in the Strand and Fleet Street; but
then it was obvious from the dinginess of their aspect that their
feathers partook of the filth of that sooty atmosphere. Martins are by
far the least agile of the four species; their wings and tails are short,
and therefore they are not capable of such surprising turns and quick and
glancing evolutions as the swallow. Accordingly they make use of a
placid easy motion in a middle region of the air, seldom mounting to any
great height, and never sweeping long together over the surface of the
ground or water. They do not wander far for food, but affect sheltered
districts, over some lake, or under some hanging wood, or in some hollow
vale, especially in windy weather. They breed the latest of all the
swallow kind: in 1772 they had nestlings on to October 21st, and are
never without unfledged young as late as M