ral control
to secure fair distribution of the water to the fields of the
inhabitants. A stimulus to progress is found in the presence of a
problem, perennial as the yearly threatenings of the Hoangho, which
demands the application of human intelligence and concerted labor for
its solution. Additional arable land for the growing population can be
secured only by the wider distribution of the fructifying water; this in
turn depends upon corporate effort wisely directed and ably controlled.
Every lapse in governmental efficiency means an encroachment of the
desert upon the alluvial fields and finally to the river bank, as to-day
in Mesopotamia.

The fact that the earliest civilizations have originated in the
sub-tropical rainless districts of the world has been ascribed solely to
the regular and abundant returns to tillage under irrigation, as opposed
to the uncertain crops under variable meteorological conditions; to the
consequent accumulation of wealth, and the emancipation of man for other
and higher activities, which follows his escape from the agricultural
vicissitudes of an uncertain climate. When Draper says: "Civilization
depends on climate and agriculture," and "the civilization of Egypt
depended for its commencement on the sameness and stability of the
African climate," and again, "agriculture is certain in Egypt and there
man first became civilized,"[614] he seizes upon the conspicuous fact of
a stable food supply as the basis of progress, failing to detect those
potent underlying social effects of the inundations--social and
political union to secure the most effective distribution of the Nile's
blessings and to augment by human devices the area accessible to them,
the development of an intelligent water economy, which ultimately
produced a long series of intellectual achievements.[615]

[Sidenote: Cultural areas in primitive America.]

This unifying and stimulating national task of utilizing and
controlling the water was the same task which in various forms prompted
the early civilization of the Hoangho and Yangtze basins, India,
Mesopotamia, Persia, Peru, Mexico, and that impressive region of
prehistoric irrigation canals found in the Salt, Gila River, and upper
Rio Grande valleys.[616] Here the arid plateaus of the Cordilleras
between the Pueblo district and Central America had no forests in which
game might be found; so that the Indian hunter had to turn to
agriculture and a sedentary life beside his n