THE PACIFIC OCEAN ITS DEPTH AND CONFIGURATION OF ITS BED The Pacific Ocean has not, for obvious reasons, been so minutely explored as the Atlantic, and was formerly supposed to be, on the whole, inferior in depth to the latter ocean. The recent observations of the Challenger, Gazelle, and Tuscarora, however, proved that this supposition is incorrect, and that, notwithstanding the immense number of islands scattered over the Western Pacific, the general depth of that ocean is fully equal to, if not exceeding, that of the Atlantic. The greatest known depth in the Atlantic is 3875 fathoms, but in the Pacific the Tuscarora obtained several soundings over 4000 fathoms ; the greatest depth, however, was found by the Challenger in 1875, between the Carolines and the Ladrones, in 24' N. lat., and 143° 16' E. long., where a sounding of 4575 fathoms, or about si miles, was obtained.
As regards the configuration of its bottom, the Paolo may be broadly divided into four basins, the limits of which may be roughly marked as follows : (i) The North-Eastern basin, limited on the north by Kamtchatka, Aleutian Isles, and Alasice, and on the east by the American coast from Alaska to Chili. A line drawn from Japan to the Sandwich Islands, and thence by the Marquesas, Gambier Island, Easter Island, Juan Fernandez, to Chili, forms the western and southern limits of this basin, distinguished from all the other basins by an almost entire absence of islands, the only groups at any distance from the coast being the Galapagos and Revillagigedo Islands. Along its western limits a depth of 3000 fathoms is frequently attained ; while in its northern portion, off Japan, a depth of over 4000 fathoms has been found. (2) The Southern basin of the Pacific may be said to extend from the limit of drift ice on the south, to the submarine ridge which divides it from the north-eastern basin. On the north are two un equal "bights," a minor elongated one between East Australia and New Zealand, and a wider bight, bounded by a line of islands—New Zealand, Friendly, Cook, Austral, Easter, and Juan Fernandez. The ridge of which these islands are the
summits unites broadly with the coasts of Chili and Pata gonia. In its deeper parts, this plateau does not seem to be depressed lower than about 1,500 fathoms below the surface, and the general depth of the basin it encloses is about 2000 fathoms. (3) What may be termed the Central basin is indeed but a westerly prolongation of the North-Eastern basin, and is bounded on the west by a chain of islands from Samtchatka, by Japan. Ladrones, Carolinas, Marshall, and Feejee Islands, to New Zealand. This basin, although studded with numerous islands, is yet of a much greater average depth than either of the other basins which it subjoins—a large portion having an average depth of 3000 fathoms. But perhaps the most marked of all the Pacific basins is (4) the Western basin, lying between the chain of islands just mentioned and the eastern coasts of Asia, and consisting for the most part of shallow and nearly land-locked basins, such as the Seas of Okhotsk, Japan, Yellow and China, and the numerous seas of the Malay Archipelago. One portion of this basin, however— that of the Sea of Magallanes, lying between the Benin, Ladrone, and Caroline Islands on the east, and the Philip pines on the west, and extending meridionally from Pelew Islands to Japan—is not inferior in depth to any of the other great basins, its average depth being about 3,000 fathoms. This basin is important, as being to the Pacific what the Caribbean Sea and the Gulf of Mexico are to the Atlantic— the cul de sac whence issues the great thermal current of the Pacific—a current which, although its climatical influence is not so well marked as its counterpart in the Atlantic, is yet by far the most important in the "Grand Ocean."