ecomes the outward expression of a
whole complex of economic wants, intellectual needs, and political
ambitions. It is embodied in the conquests which build up empires, in
the colonization which develops new lands, in the world-wide exchange of
commodities and ideas which lifts the level of civilization till this
movement of peoples becomes a fundamental fact of history.

Otis Mason finds that the life of a social group involves a variety of
movements characterized by different ranges or scopes: (1) The daily
round from bed to bed. (2) The annual round from year to year, like that
of the Tunguse Orochon of Siberia who, in pursuit of various fish and
game, change their residence within their territory from month to month,
or the pastoral nomads who move with the seasons from pasture to
pasture. (3) Less systematic outside movements covering the tribal
sphere of influence, such as journeys or voyages to remote hunting or
fishing grounds, forays or piratical descents upon neighboring lands,
eventuating usually in conquest, expansion into border regions for
occasional occupation, or colonization. (4) Participation in streams of
barter or commerce. (5) And, at a higher stage, in the great currents of
human intercourse, experience, and ideas, which finally compass the
world. In all this series the narrower movement prepares for the
broader, of which it constitutes at once an impulse and a part.

Civilized man is at once more and less mobile than his primitive
brother. Every advance in civilization multiplies and tightens the bonds
uniting him with his soil, makes him a sedentary instead of a migratory
being. On the other hand, every advance in civilization is attended by
the rapid clearing of the forests, by the construction of bridges and
interlacing roads, the invention of more effective vehicles for
transportation whereby intercourse increases, and the improvement of
navigation to the same end. Civilized man progressively modifies the
land which he occupies, removes or reduces obstacles to intercourse, and
thereby approximates it to the open plain. Thus far he facilitates
movements. But while doing this he also places upon the land a dense
population, closely attached to the soil, strong to resist incursion,
and for economic reasons inhospitable to any marked accession of
population from without. Herein lies the great difference between
migration in empty or sparsely inhabited regions, such as predominated
when the world