GENERAL VIEW OF THE CURRENTS OP THE OCEAN As the subject of "oceanic circulation," and more es pecially the causes of ocean-currents, cannot be discussed with out referring frequently to particular currents, the student should, therefore, have some knowledge of the position and direction of the principal currents before attempting to inves tigate their origin. The accompanying chart shows clearly the position and direction of the chief currents, and should be carefully studied. Commencing in the south, we have a general drift of the cold waters of the Antarctic Ocean into the Pacific —from New Zealand to Cape Horn—where the drift divides, one branch flowing round it eastwards into the Atlantic, while the other proceeds along the western coast of South America as the Peruvian current, and finally merges into the southern portion of the equatorial current of the Pacific, which sweeps across to the Malay Archipelago. One branch, the Japanese current, runs north-east along the coasts of China and Japan, and, extending to the opposite shores of North America, is then deflected south. A portion of this current forms the M ex icon current, which runs along the Mexican coast to the equator, but the main stream curves to the west, forming the northern portion of the equatorial current. The numerous streams pressing from the Pacific into the Indian Ocean, through various channels in the East Indian Archipelago, combine and form a similar northern and southern equatorial current. The former sweeps through the Bay of Bengal and the Arabian Sea, in a westerly or easterly direction ; the latter curves south along the African coast, passing through Mozambique Channel towards Cape Agulhas. A branch of the latter current curves south-west by the Mauritius, and, pressing along the eastern coast of Madagascar, unites with the main current. The combined stream now flows towards the Cape of Good Hope as the Agulhas current, one portion of which holds on its way up the Atlantic into the great equatorial current, while the remainder is turned back as a southern connecting current from the Atlantic into the Indian Ocean. The Atlantic equa torial current sweeps to the west, and deflects off Cape St. Roque, one branch turning south along the Brazilian coast, while the other trends north-west into the Caribbean Sea and the Gulf of Mexico, whence it issues as the celebrated Gulf Stream, This vast current was formerly supposed to hold on its way to the British and Norwegian coasts ; but the real current becomes diffused and scarcely recognisable a short distance off Newfoundland. The warm waters that bathe the
coasts of north-western Europe are, most probably, a general drift of the Atlantic water towards the north-east. A per ceptible drift south, between the Azores and the Spanish coast, acquires a more marked character, as it gradually trends south by Madeira and the Canary Islands, and forms the Guinea current, which, following the curves of the African coast, finally unites with the great equatorial current. Two polar currents, also, flow into the Atlantic—one from Baffin Bay, through Davis' Strait, and another along the eastern coast of Greenland. Combining off Cape Farewell, this Arctic current curves by Newfoundland and flows along the American coast, forming .a belt of cold water along the shore, bounded by the warm waters of the Gulf Stream, underneath which it finally sinks, entering the Mexican Gulf as an under-current through the Straits of Florida.
A few remarks as to the similarity between the principal currents in each ocean may serve to fix them in the memory. Thus the great equatorial currents of the Pacific, Atlantic, and Indian Oceans are all two-fold ; the northern and southern branches being separated by a minor counter current flowing east. The Gulf Stream of the Atlantic resem bles in many respects the Japanese current of the Pacific. Both have a north-easterly direction ; both terminate in nearly the same latitude ; one portion of their water uniting with a general north-east drift, while the rest is deflected off the opposite coasts into the equatorial currents. The Atlantic communicates with the Arctic by two broad chan nels, but the Pacific is nearly closed on the north, the only outlet being a strait of no considerable width or depth. Thus while the Atlantic receives the icy cold polar waters through Davis' Strait and East Greenland Channel, the com paratively shallow Behring Strait can only admit a limited amount of cold water from the Arctic into the Pacific, and is besides almost entirely occupied by a warm current flowing to the north. And as, from whatever part of the ocean a current runs, to that part an equal current must return,—all the great currents have compensating counter-currents. Thus the flow along the equator to the Mexican Gulf, in the Atlantic, is returned by the Gulf Stream and Guinea current ; and the same equatorial flow in the Pacific is compensated by the equatorial counter-current, and the eastward extension of the Japanese current.'