It was the great intellectual service of Copernicus that he conceived of a world in motion instead of a world at rest.  So anthropo-geography must see its world in motion, whether it is considering English colonization, or the westward expansion of the Southern slave power in search of unexhausted land, or the counter expansion of the free-soil movement, or the early advance of the trappers westward to the Rockies after the retreating game, or the withdrawal thither of the declining Indian tribes before the protruding line of white settlement, and their ultimate confinement to ever shrinking reservations.  In studying increase of population, it sees in Switzerland chalet and farm creeping higher up the Alp, as the lapping of a rising tide of humanity below; it sees movement in the projection of a new dike in Holland to reclaim from the sea the land for another thousand inhabitants, movement in Japan’s doubling of its territory by conquest, in order to house and feed its redundant millions.

The whole complex relation of unresting man to the earth is the subject matter of anthropo-geography.  The science traces his movements on the earth’s surface, measures their velocity, range, and recurrence, determines their nature by the way they utilize the land, notes their transformation at different stages of economic development and under different environments.  Just as an understanding of animal and plant geography requires a previous knowledge of the various means of dispersal, active and passive, possessed by these lower forms of life, so anthropo-geography must start with a study of the movements of mankind.

[Sidenote:  Mobility of primitive peoples.]

First of all is to be noted an evolution in the mobility of peoples.  In the lower stages of culture mobility is great.  It is favored by the persistent food-quest over wide areas incident to retarded economic methods, and by the loose attachment of society to the soil.  The small social groups peculiar to these stages and their innate tendency to fission help the movements to ramify.  The consequent scattered distribution of the population offers wide interstices between encampments or villages, and into these vacant spaces other wandering tribes easily penetrate.  The rapid decline of the Indian race in America before the advancing whites was due chiefly to the division of the savages into small groups, scattered sparsely over a wide territory.  Hunter and pastoral peoples need far more land than they can occupy at any one time.  Hence the temporarily vacant spots invite incursion.  Moreover, the slight impedimenta carried by primitive folk minimize the natural physical obstacles which they meet when on the march.  The lightly equipped war parties of the Shawnee Indians used gorges and gaps for the passage of the Allegheny Mountains which were prohibitive to all white pioneers except the lonely trapper.  Finally, this mobility gets into the primitive mind.  The Wanderlust