I cannot very well answer, but so many
instances of the kind have been observed as to leave no doubt as to the
fact. It has sometimes been known even to penetrate into the house, and
attach its nest to articles of furniture.

"At Camerton Hall, near Bath, a pair of swallows built their nest on the
upper part of the frame of an old picture over the chimney; and, coming
into the room through a broken pane in one of the windows, they
continued to use the same place for their nest for three successive
years, and would probably have continued to do so, but the room having
been put into repair, they could no longer obtain access to it."

"Is it want of food which makes birds migrate, Uncle Thomas?"

"Principally, I should say that it is so, Frank, but in shifting from
one place to another they only fulfil an instinct impressed on them by
their Creator for the preservation of their species. Thus, for instance,
an old swallow might know by experience, that when its food fails here,
it begins to become plentiful elsewhere, but the young bird which had
never been more than a few miles from the place where it was hatched,
can have no such experimental knowledge; yet, when the season arrives,
we find the whole flock ready to set out. I dare say you have all seen
them, Boys, gathering in flocks and resting on the house tops, as if
taking breath before setting out on their long journey."

"Oh, yes, Uncle Thomas, I have often seen them doing so, but I have
heard that they dive to the bottom of lakes and ponds, and remain there
till winter is over."

"Many foolish stories are told of swallows being found in such
situations, Harry, but they are now well known to be fables. There is no
doubt that they migrate in the same way as many other birds. Last autumn
I watched with great pleasure the movements of a flock, which was
evidently preparing for their arduous flight.

"For several evenings they assembled in large numbers on a tree at a
short distance from my house, and, after remaining seated for some time,
one of them, who appeared to be commander-in-chief, kept flying about
in all directions, and at length, with a sharp and loudly repeated call,
he darted up into the air. In an instant the whole congregation were on
the wing, following their leader in a sort of spiral track. In a little
time they had risen so high that I lost sight of them, but after a short
absence they again returned and took up their position on the tree which