mile; practised with European methods in young or colonial lands, as in
Arkansas, Texas, Minnesota, Hawaii, Canada and Argentine, or in European
lands with unfavorable climate, up to 25 to the square mile.

Pure agricultural lands of central Europe support 100 to the square
mile, and those of southern Europe, 200; when combining some industry,
from 250 to 300. But these figures rise to 500 or more in lowland India
and China. Industrial districts of modern Europe, such as England,
Belgium, Saxony, Departments Nord and Rhone in France, show a density of
500 to 800 to the square mile. [See maps pages 8 and 9.]

[Sidenote: Density of population and government.]

With every increase of the population inhabiting a given area, and with
the consequent multiplication and constriction of the bonds uniting
society with its land, comes a growing necessity for a more highly
organized government, both to reduce friction within and to secure to
the people the land on which and by which they live. Therefore
protection becomes a prime function of the state. It wards off outside
attack which may aim at acquisition of its territory, or an invasion of
its rights, or curtailment of its geographic sphere of activity. The
modern industrial state, furthermore, with the purpose of strengthening
the nation, assists or itself undertakes the construction of highways,
canals, and railroads, and the maintenance of steamship lines. These
encourage the development of natural resources and of commerce, and
hence lay the foundation for an increased population, by multiplying the
relations between land and people.

[Sidenote: Territorial expansion of the state.]