MIGRATION. 279 
CHAPTER XXII. 
MIGRATION OF BIRDS. 
Few subjects connected with natural history are 
more interesting, or have more attracted the atten- 
tion of ordinary observers, than the periodical ap- 
pearance and disappearance of certain species of 
birds. These curious phenomena have been no- 
ticed in all ages and countries; the sages of old, as 
well as the scientific of our own days, have looked 
upon them with interest; and to the agriculturist, 
the shepherd, and all whose occupations lead them 
to the fields, the woods, or the hills, they are in 
some measure familiar. Even the inspired seer 
has found in them an illustration suited to his pur- 
pose: “ The stork in the heaven,” says the prophet. 
Jeremiah, ‘“‘ knoweth her appointed times; and the 
turtle, and the crane, and the swallow observe the 
time of their coming ” 
The regular appearance and disappearance of 
some species of birds excited the curiosity of ob- 
servers in all ages, and led to many conjectures re- 
specting its causes. It was long alleged and be- 
lieved that swallows, instead of removing to warmer 
climates, lie concealed in fissures of rocks, in sand-~ 
banks, in the holes of decayed trees, and even at 
the bottom of the water in ponds, femaining during 
the winter in a torpid state. “It is certain,” says 
the Dutch naturalist Jonston, “ that in hollow trees, 
lying many close together, they preserve them- 
selves by mutual heat.” “In certain woods of Up- 
per Germany,” says the author of the Physice 
Curiose, “upon cutting up a rotten oak-tree, it has 
been found fuil of swallows.” He does not quote 
