eographic forces, varying from inland basin to marginal sea, from
marginal sea to open ocean, and changing from one historical period to
another--an interplay so mercurial that it could find only a most
inadequate expression in the rigid mathematical formula of Carl Ritter.

[Sidenote: Accessibility of coasts from hinterland.]

As the coast, then, is the border zone between the solid, inhabited land
and the mobile, untenanted deep, two important factors in its history
are the accessibility of its back country on the one hand, and the
accessibility of the sea on the other. A littoral population barred from
its hinterland by mountain range or steep plateau escarpment or desert
tract feels little influence from the land; level or fertile soil is too
limited in amount to draw inland the growing people, intercourse is too
difficult and infrequent, transportation too slow and costly. Hence the
inhabitants of such a coast are forced to look seaward for their racial
and commercial expansion, even if a paucity of good harbors limits the
accessibility of the sea; they must lead a somewhat detached and
independent existence, so far as the territory behind them is concerned.
Here the coast, as a peripheral organ of the interior, as the outlet
for its products, the market for its foreign exchanges, and the medium
for intercourse with its maritime neighbors, sees its special function
impaired. But it takes advantage of its isolation and the protection of
a long sea boundary to detach itself politically from its hinterland, as
the histories of Phoenicia, the Aegean coast of Asia Minor, Dalmatia,
the republics of Amalfi, Venice, and Genoa, the county of Barcelona, and
Portugal abundantly prove. At the same time it profits by its seaboard
location to utilize the more varied fields of maritime enterprise before
it, in lieu of the more or less forbidden territory behind it. The
height and width of the landward barrier, the number and practicability
of the passways across it, and especially the value of the hinterland's
products in relation to their bulk, determine the amount of intercourse
between that hinterland and its mountain or desert barred littoral.

[Sidenote: Mountain-barred hinterlands.]

The interior is most effectively cut off from the periphery, where a
mountain range or a plateau escarpment traces the inner line of the
coastland, as in the province of Liguria in northern Italy, Dalmatia,
the western or Malabar coast of Ind