Far to the north the Atlantic penetrates the American continent by Davis’s Straits, and spreads out into Baffin’s bay, twice the size of the Baltic, very deep, and subject to all the rigours of an arctic winter—the very storehouse of icebergs—the abode of the walrus and the whale. Hudson’s Bay, though without the Arctic Circle, is but little less dreary. Very different is the character of those vast seas where the Atlantic comes “cranking in” between the northern and southern continents of America. The surface of the sea in Baffin’s Bay is seldom above the freezing-point; here, on the contrary, it is always 88°·5 of Fahrenheit, while the Atlantic Ocean in the same latitude is not above 77° or 78°. Of that huge mass of water, partially separated from the Atlantic by a long line of islands and banks, the Caribbean Sea is the largest; it is as long from east to west as the distance between Great Britain and Newfoundland, and occupies a million of square miles. Its depth in many places is very great, and its water is limpid. The Gulf of Mexico, fed by the Mississippi, one of the greatest of rivers, is more than half its size, or about 625,000 square miles, so that the whole forms a sea of great magnitude. Its shores, and the shores of the numerous islands, are dangerous from shoals and coral-reefs, but the interior of these seas is not. The trade-winds prevail there; they are subject to severe northern gales, and some parts are occasionally visited by tremendous hurricanes. By the levelling across the peninsula of Panama by Mr. Lloyd, in 1828, the mean height of the Pacific above that of the Atlantic was found to be three feet six inches. The Pacific does not penetrate the land in the same manner that the Atlantic does the continent of Europe. The Red Sea and Persian Gulf are joined to it by very narrow straits; but almost all the internal seas on the eastern coast of Asia, except the Yellow Sea, are great gulfs shut in by islands, like the Caribbean Sea and the Gulf of Mexico, to which the China Sea, the Sea of Japan, and that of Okhotsk are perfectly analogous. The set of the great oceanic currents has scooped out and indented the southern and eastern coasts of the Asiatic continent into enormous bays and gulfs, and has separated large portions of the land, which now remain as islands—a process which probably has been increased by the submarine fires extending along the eastern coast from the equator nearly to the Arctic Circle. The perpetual agitation of the ocean by winds, tides, and currents, is continually, but slowly, changing the form and position of the land— steadily producing those vicissitudes on the surface of the earth to which it has been subject for ages, and to which it will assuredly be liable in all time to come. CHAPTER XVII. Springs—Basins of the Ocean—Origin, Course, and Heads of Rivers— Hydraulic Systems of Europe—African Rivers—the Nile, Niger, &c.