PACIFIC OCEAN 



691 



South America, and proceeding northwards along 

 the American coast, then southwards along the 

 Asiatic coast, we have Tierra del Kuego and the 

 islands off the coast of Chili ; Vancouver, Queen 

 Charlotte, Prince of Wales, and other islands off 

 the coast of British North America ; Kodiak Island, 

 off the Alaskan coast ; the Aleutian chain of 

 islands, stretching from the Alaskan peninsula 

 towards the Asiatic coast and enclosing Behring 

 Sea; the Kurile Islands, stretching from the 

 peninsula of Kamchatka to the Japanese Islands ; 

 Saghalien ; the islands of Japan ; Formosa and 

 Hainan, off the Chinese coast; the Philippine 

 Islands ; Borneo, Celebes, Sumatra, Java, and 

 other islands of the East Indian Archipelago ; New 

 Guinea ; New Caledonia ; Australia and Tasmania ; 

 and New Zealand. The oceanic islands of the 

 Pacific are all either of volcanic or coral origin, 

 the volcanic islands lying within the zone of coral- 

 reef builders being fringed with coral-reefs, while 

 there are large numbers of islands entirely of coral 

 formation coral atolls. The principal groups are 

 the Hawaiian Islands, in the centre of the North 

 Pacific basin, 18 to 22 N. lat., consisting of eight 

 larger and four smaller islands, containing manv 

 active and extinct volcanoes, including the well- 

 known Kilauea in Hawaii, said to be the largest 

 active crater in the world ; the Bonin Islands, 

 south-east of Japan ; the Ladrone or Mariana 

 Islands, Ijetween 13 and 20 N. lat., containing 

 several active volcanoes; the Caroline Islands, 

 south of the Ladrones, mostly of coral formation ; 

 the Marshall Islands, east of the Carolines, entirely 

 of coral formation ; the Gilbert Islands, on the 

 equator, of coral formation and densely populated ; 

 in the South Pacific there are the Solomon Islands, 

 the New Hebrides, the Fiji Islands, the Friendly 

 Islands, the Samoa or Navigator Islands, the 

 Society Islands, all fringed by coral-reefs, and the 

 Paumotu or Low Archipelago, an extensive group 

 of coral islands lying between 10 and 25 S. lat., 

 besides the volcanic Galapagos group on the equator 

 about 600 miles off the coast of Ecuador, and others 

 of less extent and importance. 



Depth. The Pacific was formerly looked upon as 

 rather a shallow ocean, but we now know that some 

 of the greatest depths in the world occur in it, and 

 that on the whole it is deeper than the Atlantic, 

 its mean depth being about 2500 fathoms. The 

 eastern basin is comparatively uniform in depth, 

 between 2000 and 3000 fathoms, except a large 

 area under 2000 fathoms extending from off the 

 coast of Chili in a westerly direction for over 40 of 

 longitude, while off the north-west coast of North 

 America the 2000 fathom line lies a considerable 

 distance off-shore. The western basin is much 

 more diversified, numerous groups of islands, 

 shallow water, and immense depths occurring 

 irregularly ; the greatest depths yet sounded are 

 found in this region of the Pacific. The Challenqer's 

 deepest sounding, 4575 fathoms (nearly 5 J miles), 

 was in the sea between the Caroline and Ladrone 

 Islands, while the American ship Tuscarora found 

 a depth of 4655 fathoms to the north-east of Japan, 

 where a large area of very deep water extends off 

 the Kurile Islands and Japanese coast ; more 

 recently depths of over 4000 fathoms have l?en 

 discovered off the coast of Chili, and a British 

 surveying ship has sounded in 4530 fathoms east 

 of the Fiji Islands, which is the deepest sounding 

 recorded south of the equator. There are many 

 detached patches throughout the Pacific with 

 depths of over 3000 fathoms. The seas lx>rder- 

 Ing on the western basin of the Pacific vary 

 considerably in depth : the depth in the Sea of 

 Okhotsk, the Yellow Sea, and the Java Sea does 

 not apparently exceed 700 fathoms ; and the 

 Behring Sea, the Sea of Japan, and the Arafura 



Sea are all under 1500 fathoms ; while the China 

 Sea, Celebes Sea, Sulu Sea, and the Banda Sea 

 are in some places over 2000 fathoms in depth. 

 The bulk of water filling the Pacific is estimated 

 at 170,000,000 cubic miles. 



Winds and Cut-rents. The surface-currents of 

 the Pacific Ocean depend to a great extent upon 

 the direction of the prevailing winds, the principal 

 of which are the two trade-winds, blowing more or 

 less constantly, the one from the north-east, the 

 other from the south-east. Between these two 

 regions is what is called the equatorial belt of 

 calms, which is found all the year round north of 

 the equator in the eastern Pacific, but in the west 

 Pacific it is south of the equator during the summer 

 of the southern hemisphere, and during the southern 

 winter it is replaced by a regular southerly breeze ; 

 north and south of the trade-winds, also, there are 

 two other belts of calms. In addition to the trade- 

 winds, there are the monsopns, which blow with 

 great regularity, but the direction of which changes 

 according to the season. Monsoons are especially 

 prevalent in the west Pacific, their general direc- 

 tion being south-east, north-east, or north-west, 

 and they cause surface-currents, the direction of 

 which likewise changes with the season. The 

 differences between the temperature and atmo- 

 spheric pressure over the land and over the water 

 cause monsoonal winds. In mid-ocean the winds 

 are found to have a greater velocity than in the 

 vicinity of the land. 



The Pacific is practically cut off, as far as the 

 circulation of the deep water is concerned, from com- 

 munication with the Arctic Ocean in the north, but 

 towards the south it has uninterrupted communi- 

 cation with the Antarctic. A cold surface-current 

 Hows constantly northwards from the Antarctic, 

 dividing into two at Cape Horn, one entering 

 the Atlantic, the other flowing along the coasts of 

 Chili and Peru, thence turning to the westwards ; 

 but the cold water frequently met with along the 

 eastern coasts of America is evidently brought from 

 oceanic depths by the action of off-shore winds. 

 The great equatorial current flows to the west- 

 ward, divided by a counter-current running in an 

 opposite direction into two branches, the northern 

 one on approaching the Asiatic coast being de- 

 flected northwards and finally north-eastwards as 

 the Japan current, which is comparable to the 

 Gulf Stream in the Atlantic ; the southern branch 

 is diverted to the southward, flowing along the 

 shores of Australia and New Zealand, thence curv- 

 ing eastwards, and ultimately merging into the 

 Antarctic surface-current. There are many minor 

 currents, and branches of these more important 

 ones, diverted by the numerous groups of islands. 

 The broad currents, circling in the one direction in 

 the North Pacific and in the opposite direction in 

 the South Pacific, enclose in their centres two 

 miniature Sargasso Seas somewhat similar to 

 that of the North Atlantic, though not so well 

 marked. 



Temperature of the Water. The temperature of 

 the surface-waters of the Pacific varies with the 

 season, but in the tropical regions the variation is 

 very small. Between the latitudes of 45 N. and 

 45 S. the temperature of the surface is always 

 above 50 F., while north and south of these lati- 

 tudes it is nearly always below 50 F. The highest 

 temperature occurs among the islands of the Malay 

 Archipelago and off the Mexican coast, where the 

 mean temperature rises to 85 F., and in the sea 

 between Japan and New Guinea the temperature 

 in August reaches 84 F. In the South Pacific 

 the temperature of the surface-water is appar- 

 ently higher than that of the air, while in the 

 North Pacific the reverse is the case in some places. 

 The temperature of the water below the surface 



