a house that stood near the river, and while talking with the people
within doors, I was suddenly struck with astonishment at a loud rushing
roar, succeeded by instant darkness, which for the first moment I took
for a tornado about to overwhelm the house, and every thing around, in
destruction. The people observing my surprise, coolly said, 'It is only
the pigeons,' and on running out, I beheld a flock thirty or forty yards
in width, sweeping along very low between the house and the mountain or
height that formed the second bank of the river. These continued
crossing for more than a quarter of an hour, and at length varied their
bearing, so as to pass over the mountain, behind which they disappeared
before the rear came up."

"That is amazing, Uncle Thomas; two thousand millions of live birds! I
can scarcely form an adequate idea of such a mass of living creatures."

"There is something almost overwhelming in the idea, Frank; and yet in
some parts of the world are to be found flocks of animals hardly less
surprisingly numerous, when we consider how much less they are fitted
for moving about, travelling at stated intervals from the mountains to
the sea coast, and returning again to their old habitations, after
having fulfilled the purposes for which this instinctive feeling was
implanted in them."

"Which animals do you mean, Uncle Thomas?"

"I allude to the land-crab, which is a native of the Bahamas, and also
of most of the other islands between the tropics. They live in clefts of
the rocks, or holes which they dig for themselves among the mountains,
and subsist on vegetables. About the months of April and May, they
descend to the sea coast in a body of millions at a time, for the