To the student of the geography of a continent the climatic and other influences of the great ocean currents, as well as the more tangible results produced by the waves which break on the borders of the land, demand extended and painstaking investigation. The most that we can hope to do at present in this connection is to state briefly some of the more important influences that the movements of the ocean waters have on the climate of North America and on the topography of its shores. _Currents._--The surface waters of both the north Atlantic and the north Pacific, as is the case with all broad water bodies, have a drift and in places flow in well-defined currents, mainly on account of the friction of the wind on the surface of the sea, aided by variations in the density of the water due to differences in temperature and salinity. In each ocean there is a great swirl or eddy, for the reason that the surface drift and the flow of the deeper currents carry the waters about in a rudely circular path, parallel in a general way with the boundaries of the respective basins. The direction of this motion, to one situated in the central part of either basin, is from left to right, or with the movements of the hands of a watch. In the southern portion of each basin there is a westward-flowing equatorial current, which in each instance is deflected northward on approaching the bordering land, and as it continues is still more deflected owing to the influence of the earth's rotation, and acquires a northeast trend; on reaching the eastern side of the oceanic basins, the currents are again deflected, a portion of the one in the Atlantic and all of the one in the Pacific being turned southward so as to complete the circuit. In the southern portion of the north Atlantic the surface drift is westward at a rate of four or five miles a day. The waters, forced along principally by the trade-winds, flow through the numerous passes between the Lesser Antilles and enter the Caribbean Sea, and from thence are carried through the Yucatan channel into the Gulf of Mexico. The waters are piled up, as it were, in that great landlocked basin, at the same time becoming warmer, and receive additions of fresh water from rain and inflowing streams. Each of these causes tends to decrease the density of the water, while evaporation has a counterbalancing influence. The escape for the waters, both salt and fresh, which enter the Gulf, is by evaporation and by flowing through the only notch in the rim of the Gulf basin which is not in the path of the equatorial current, namely, the strait separating Florida from Cuba and the Bahama Islands. These outflowing waters form the justly celebrated Gulf Stream.