In the Arctic Ocean the tides are small. At Point Barrow, the most northern locality on the coast of Alaska, the difference between high and low water is but 6 or 7 inches. The tide comes from the southward and westward, and there is a prevailing current setting to the eastward. At Herschel Island, near where the east boundary of Alaska reaches the Arctic Ocean, the mean range of the tide is but 1.8 foot. At Cape Sheridan, the northeast point of Grinnell Land, north latitude 82 deg. 25', there is a range of 2.6 feet during two periods each month when the tides are highest, and but 1.2 foot at the lowest or neap tide periods. In addition to the weakness of the tides and tidal currents along the arctic coast, there is an absence or great diminution of the influence of wave and currents, owing to the prevalence of ice on the sea. Shore erosion is there at a minimum in spite of the abrasion produced by the ice-packs when forced landward by the wind. _Islands._--In the classification of islands used by A. R. Wallace in his Island Life two primary divisions are recognised, namely, continental and oceanic islands. Continental islands are land masses which have been separated from continents and are rarely far removed from their borders, and, besides, are composed of rocks similar to those of the neighbouring mainland and inhabited by terrestrial animals which are related to the fauna of the larger land area. Ancient and modern continental islands have also been recognised, their age being indicated by the degree of similarity between their faunas and the fauna of the continent with which they were formerly connected. Those of ancient origin are commonly surrounded by deep water, while those which are more modern usually rise from continental shelves, the channels intervening between them and the mainland being less than 100 fathoms deep. Oceanic islands rise from deep water, are either volcanic or so far as their emerged portions are concerned composed of coral rock, and are without warm-blooded terrestrial animals. About the borders of North America there are islands belonging to each of these classes. The numerous examples rising from the continental shelf all about the margin of the land, but in the Atlantic most numerous from New York northward, and in the Pacific from the Strait of Fuca northward, are plainly recent continental islands. The larger of the West Indies and the group of small islands off the California coast are also continental islands, but show by the character of their faunas and the depth of the water about them that they have been long separated from the main mass of the continent. Typical examples of oceanic islands are furnished by Bermuda, in the Atlantic, and Guadalupe, in the Pacific. In this same class, but less remote from the mainland, and in their faunas and floras showing a nearer relationship to South than to North America, belong the Caribbees. TOPOGRAPHY OF THE COAST