the beginning of Caesar's exploits. What men do only at intervals birds do frequently, having greater freedom of movement.
Who can doubt that the wild fowl come south because the north is frozen over? The Laplander and the reindeer migrate together; the Tartars migrate all the year through, crossing the steppes in winding and devious but fixed paths, paths settled for each family, and kept without a map, though invisible to strangers. It is only necessary to watch the common sparrow. In spring his merry chirp and his few notes of song are heard on the roof or in the garden; here he spends his time till the broods are reared and the corn is ripe. Immediately he migrates into the fields. By degrees he is joined by those left behind to rear second broods, and at last the stubble is crowded with sparrows, such flocks no one would believe possible unless they had seen them. He has migrated for food, for his food changes with the season, being mainly insects in spring, and grain and seeds in autumn. Something may, I venture to think, in some cases of migration, be fairly attributed to the influence of a desire for change, a desire springing from physiological promptings for the preservation of health. I am personally subject twice a year to the migratory impulse. I feel it in spring and autumn, say about March, when the leaves begin to appear, and again as the corn is carried, and most strongly as the fields are left in stubble. I have felt it every year since boyhood, often so powerfully as to be quite unable to resist it. Go I must, and go I do, somewhere; if I do not I am soon unwell. The general
