Page:The American Cyclopædia (1879) Volume XII.djvu/795

PACIFIC OCEAN 781 can shore is remarkably uniform and almost unbroken, except by the fiords of Patagonia, British America, and Alaska, and by the gulf of California. The 1ST. and W. shores are bro- ken into innumerable islands, separating its waters from a chain of inland seas, such as Behring sea, the Okhotsk, Japan, and Yellow seas, the E. and S. China seas, and the Banda, Arafura, and Coral seas. This configuration has had a great influence on the migration of the populations, and on the comparatively high and early civilization of some of them, such as the Chinese and Japanese. The depth of this ocean is not yet known in much de- tail. By means of the recorded time of trans- mission to California of the waves produced by an earthquake in Japan, Prof. Bache calcu- lated the depth as between 2,000 and 2,400 fathoms. Another calculation based on the movement of the waves of the great South American earthquake of 1868, by Prof. Hoch- stetter, gave somewhat less than 2,000 fath- oms. The soundings made in 1874 by Com. Belknap in the United States steamer Tuscaro- ra, between California, the Hawaiian islands, and Japan, give an average very near Prof. Bache's results, a brilliant confirmation of Prof. Airy's formula on which the calculations were based. The maximum depth is about 3,000 fathoms. Similar depths were found by the Challenger expedition (1874) in the south Pacific, and in the Melanesian, Celebes, and Sooloo seas ; in these latter the decrease of temperature with depth ceased at a point of equal depth with the lowest part of the rim of the submarine basin enclosing them, and be- low this the temperature remained constant ; a phenomenon similar to that observed in the Mediterranean. The soundings of the Chal- lenger in the Pacific confirm the observations made by the same party in the Atlantic, viz., that below 2,250 fathoms on an average the gloMgeriva deposits are no longer found, the bottom consisting of red clay. The currents resolve themselves into two systems, as in the Atlantic. The southern one in its gene- ral features forms a revolving stream turning from right to left, the northern one revolving in the contrary direction. The former origi- nates in the southwest and south by the combi- nation of the south Australian current, coming from the Indian ocean, with the great antarc- tic drift. This current moves E., crossing the whole breadth of the ocean toward the coast of South America; before reaching it, it divides into two branches, the northern or current of Mentor trending N. E. until it reaches about Ion. 78 W., when it turns "W. in a wide sweep to join the S. equatorial current. The south- ern branch strikes the American coast, gives off the Cape Horn current, passing around that cape into the Atlantic, then runs N., hug- ging the coast under the name of the Humboldt or Peruvian current, nearly up to the equator, where it turns W. and crosses the whole of the ocean as the S. equatorial current, following nearly the parallel of 10 S. The Humboldt current, receiving much of its water from the antarctic regions, is cold, and reduces the tem- perature of the South American coast much below the degree due to the latitude. At the Galapagos islands Qapt. Fitzroy found the temperature of the water only 60, while just outside the group on the north it was 80 in the water coming from the direction of the bay of Panama. The S. equatorial current divides into several branches in the vicinity of the Tonga islands, one of them running into Tor- res strait, and another along the E. coast of Australia, sweeping round toward New Zea- land. A little N. of the equator, a counter current is found running E. across the whole ocean and separating the N. and S. equatorial currents; this is the belt of the equatorial calms. The N. equatorial current strikes the coast of Asia near the island of Formosa, and is deflected N". and N. E., forming the Ja- pan current (Kuro-Siwo or Black stream), the counterpart of the Gulf stream of the Atlantic. It gives off the Kamtchatka current, running up toward Behring strait, but the main body crosses over toward Alaska, carrying warmth and moisture to that country, then runs S. as the coast current of California, and off the coast of Mexico returns into the equatorial circulation. The trade winds are found to blow with regularity only in that part of the ocean most free of islands. Thus the S. E. trades can be depended on only between the meridians of the Galapagos and Marquesas islands, and between the tropic of Capricorn, or at the most 30 S., and the equator or even a little N. of it. The K E. trades are chiefly confined between lat. 30 and 10 N., these limits varying somewhat with the sun's declina- tion. In longitude they are encountered about 200 leagues off the coast of America, and as far as the Ladrone islands. A belt of calms and variable winds is encountered a few degrees N. of the equator. Along the coast of America, and among the islands of Polynesia, including Melanesia and Micronesia, there are areas of periodical winds, in some parts as regular as the monsoons of the Indian ocean. On the coast of Chili northerly winds prevail from May to September, and southerly from Octo- ber to May. On the coast of California it blows from N. W. during the summer months, and from S. E. to S. W. in winter. Among the islands of Polynesia situated in the region of the S. E. trades, this wind blows regularly between March and October, while westerly winds prevail the rest of the year, with occa- sionally violent storms. Between the Ladrone and Philippine islands the monsoon is more regular, K E. from May to April, and S. W. during the other months. As in the Indian ocean, the change of the monsoons is accom- panied by storms ; but hurricanes of the type of those of the West Indies or Mauritius are not known in the greater part of the Pacific, the exception being the region W. of the La-