CURRENTS OF THE PACIFIC. n 



If an imaginary line be drawn from Honolulu to Tahiti the portion of the Pacific 

 to the east of this line is of comparatively even and moderate depth and there are few 

 islands. West of this line island groups are abundant and the bottom presents great 

 irregularities. Abysmal holes abound and submarine peaks arise in some cases many 

 thousand feet from a depressed plateau. Shallow tracts are said to extend from Pata- 

 gonia to Japan, and parallel to this occur the wrinkle-like elevations of the bottom on 

 which occur the many groups of islands. The seas that fringe the western boundary 

 of this ocean are separated from the main basin by plateaus of considerable height, 

 although still submarine, and this feature has furnished rather insecure foundation 

 (in our present knowledge) for many theories of animal and vegetable distribution. 

 A matter of considerable interest is the occurrence of deep holes such as that the 

 Challenger found between the Caroline and Marianas Groups where the soundings indi- 

 cated 4475 fathoms, or about five miles and a quarter. Another occurs east of Tonga ; one 

 has just been found near Midway Island, and the "deep" along the eastern coast of Japan 

 from 20" X. to 50" N. seems like a long narrow crack in the sea bottom. Other deeps have 

 been charted and the number which bear distinctive names is already considerable, but 

 they can best be studied in the Challenger reports and on the more recent hydrographic 

 charts. The shoals seem even more important as they may be inchoate islands. 



Currents of the Pacific. — It is certainly known that the vast body of water 

 of this ocean is in a constant state of circulation, and in a way partly independent of 

 the prevailing winds, although, as we shall see below, the winds vary with the seasons 

 as do the main channels of circulation. In this place it is sufficient to mention the 

 great streams or arteries which flow in tolerably determined bounds and in constant 

 direction while we must pass by the less definite currents which are modified by lands, 

 by shoals, or bv the winds, — currents which in meeting do not mingle, but the denser or 

 cooler current sinks below and passes beneath its lighter antagonist. 



Bering Strait is but a little gateway and admits no important current from the 

 Arctic seas, but on the south from the Antarctic regions a strong current flows north 

 to New Zealand where it is turned eastward to the coast of Patagonia, a branch con- 

 tinuing east past Cape Horn, while the main stream, called in honor of its discoverer 

 Humboldt, passes up the coast of South America until the isthmus of Panama deflects 

 it to the west. As it meets the coast of Formosa it also encounters and travels with a 

 stream analogous to the Gulf Stream of the Atlantic, the Kuro siwa of the Japanese, 

 so called from its dark blue color. Merged with this it flows northeast then east until 

 the Alaskan shores divert it to the south and west. The Kuro siwa has an average 

 maximum temperature of 86' F., or about 12° greater than that of the waters of the 

 ocean through which it passes. Narrow near Formosa, it gradually broadens until 

 north of the Bonin Group it is 500 miles wide. Between the two great equatorial cur- 

 rents flowing westward on either side of the equator is a narrow counter-equatorial 



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