Three-fifths of the maritime activity of the whole Austrian Empire is confined to the ragged coast of Dalmatia, which furnishes to-day most of the sailors for the imperial marine, just as in Roman days it manned the Adriatic fleet of the Caesars.[453] The Haida, Tsimshean, and Tlingit Indians of the ragged western coast of British Columbia and southern Alaska spread their villages on the narrow tide-swept hem of the land, and subsist chiefly by the generosity of the deep.  They are poor landsmen, but excellent boat-makers and seamen, venturing sometimes twenty-five miles out to sea to gather birds’ eggs from the outermost fringe of rocks.

[Sidenote:  Contrasted coastal belts.]

As areas of elevation or subsidence are, as a rule, extensive, it follows that coasts usually present long stretches of smooth simple shoreline, or a long succession of alternating inlet and headland.  Therefore different littoral belts show marked contrasts in their degree of accessibility to the sea, and their harbors appear in extensive groups of one type—­fiords, river estuaries, sand or coral reef lagoons, and embayed mountain roots.  A sudden change in relief or in geologic history sees one of these types immediately succeeded by a long-drawn group of a different type.  Such a contrast is found between the Baltic and North Sea ports of Denmark and Germany, the eastern and southern seaboards of England, the eastern and western sides of Scotland, and the Pacific littoral of North America north and south of Juan de Fuca Strait, attended by a contrasted history.

A common morphological history, marked by mountain uplift, glaciation, and subsidence, has given an historical development similar in not a few respects to the fiord coasts of New England, Norway, Iceland, Greenland, the Alaskan “panhandle,” and southern Chile.  Large subsidence areas on the Mediterranean coasts from the Strait of Gibraltar to the Bosporus have in essential features duplicated each other’s histories, just as the low infertile shores of the Baltic from Finland to the Skager Rack have had much in common in their past development.

Where, however, a purely local subsidence, as in Kamerun Bay and Old Calabar on the elsewhere low monotonous stretch of the Upper Guinea coast,[454] or a single great river estuary, as in the La Plata and the Columbia, affords a protected anchorage on an otherwise portless shore, such inlets assume increased importance.  In the long unbroken reach of our Pacific seaboard, San Francisco Bay and the Columbia estuary are of inestimable value; while, by the treaty of 1848 with Mexico, the international boundary line was made to bend slightly south of west from the mouth of the Gila River to the coast, in order to include in the United States territory the excellent harbor of San Diego.  The mere nicks in the rim of Southwest Africa constituting Walfish Bay and Angra Pequena assume considerable value as trading stations and places of refuge along that 1,200-mile reach of inhospitable