rim of Europe, brings Atlantic civilization to this half-Asiatic side of the continent.  The solid front presented by the Iberian Peninsula and Africa to the Atlantic has a narrow crack at Gibraltar, whence the Mediterranean penetrates inland 2,300 miles (3,700 kilometers), and converts the western foot of the Caucasus and the roots of the Lebanon Mountains into a seaboard.  By means of the Arabian Sea, the Indian Ocean runs northward 1,300 miles (2,200 kilometers) from Cape Comorin to meet the Indus delta; and then turns westward 700 miles farther through the Oman and Persian gulfs to receive the boats from the Tigris and Euphrates.  Such marine inlets create islands and peninsulas; which are characterized by proximity to the sea on all or many sides; and in the interior of the continents they produce every degree of nearness, shading off into inaccessible remoteness from the watery highway of the deep.

The success with which such indentations open up the interior of the continents depends upon the length of the inlets and the size of the land-mass in question.  Africa’s huge area and unbroken contour combine to hold the sea at arm’s length, Europe’s deep-running inlets open that small continent so effectively that Kazan, Russia’s most eastern city of considerable size, is only 750 miles (1,200 kilometers) distant from the nearest White Sea, Baltic, and Azof ports.  Asia, the largest of all the continents, despite a succession of big indentations that invade its periphery from Sinai peninsula to East Cape, has a vast inland area hopelessly far from the surrounding oceans.

[Sidenote:  Ratio of shoreline to area.]

In order to determine the coast articulation of any country or continent, Carl Ritter and his followers divided area by shoreline, the latter a purely mathematical line representing the total contour length.  By this method Europe’s ratio is one linear mile of coast to 174 square miles of area, Australia’s 1:224, Asia’s 1:490, and Africa’s 1:700.  This means that Europe’s proportion of coast is three times that of Asia and four times that of Africa; that a country like Norway, with a shoreline of 12,000 miles traced in and out along the fiords and around the larger islands,[440] has only 10 square miles of area for every mile of seaboard, while Germany, with every detail of its littoral included in the measurement, has only 1,515 miles of shoreline and a ratio of one mile of coast to every 159 square miles of area.

The criticism has been made against this method that it compares two unlike measures, square and linear, which moreover increase or decrease in markedly different degrees, according as larger or smaller units are used.  But for the purposes of anthropo-geography the method is valid, inasmuch as it shows the amount of area dependent for its marine outline upon each mile of littoral.  A coast, like every other boundary, performs the important function of intermediary in the intercourse of a land with its neighbors; hence