f adolescence shortened and, like Great Britain, early reached
its maturity. Nature itself set the goal of its territorial expansion,
and by crystallizing the political ideal of the people, made that goal
easier to reach, just as the dream of "United Italy" realized in 1870
had been prefigured in contours drawn by Alpine range and Mediterranean
shore-line.

[Sidenote: The sea as the absolute boundary]

The area which a race or people occupies is the resultant of the
expansive force within and the obstacles without, either physical or
human. Insurmountable physical obstacles are met where all life
conditions disappear, as on the borders of the habitable world, where
man is barred from the unpeopled wastes of polar ice-fields and
unsustaining oceans. The frozen rim of arctic lands, the coastline of
the continents, the outermost arable strip on the confines of the
desert, the barren or ice-capped ridge of high mountain range, are all
such natural boundaries which set more or less effective limits to the
movement of peoples and the territorial growth of states. The sea is the
only absolute boundary, because it alone blocks the continuous, unbroken
expansion of a people. When the Saxons of the lower Elbe spread to the
island of Britain, a zone of unpeopled sea separated their new
settlements from their native villages on the mainland. Even the most
pronounced land barriers, like the Himalayas and Hindu Kush, have their
passways and favored spots for short summer habitation, where the people
from the opposite slopes meet and mingle for a season. Sandy wastes are
hospitable at times. When the spring rains on the mountains of Abyssinia
start a wave of moisture lapping over the edges of the Nubian desert,
it is immediately followed by a tide of Arabs with their camels and
herds, who make a wide zone of temporary occupation spread over the
newly created grassland, but who retire in a few weeks before the
desiccating heat of summer.[339]

[Sidenote: Natural boundaries as bases of ethnic and political
boundaries.]

Nevertheless, all natural features of the earth's surface which serve to
check, retard or weaken the expansion of peoples, and therefore hold
them apart, tend to become racial or political boundaries; and all
present a zone-like character. The wide ice-field of the Scandinavian
Alps was an unpeopled waste long before the political boundary was drawn
along it. "It has not in reality been a definite natural _line_ that