North of the Pacific equator a similar westward current moves steadily over the great waste of waters past the Sandwich Islands to the coast of China. From the Philippines and Japan northward, however, there is a far stronger flow, known to the Japanese as the Black Current (Kuroshiwo), which skirts the coast of Japan and the Kurile Islands, makes these and Kamchatka habitable, then turns sharply east along the front of the foggy Aleutian chain of islands, and broadening and cooling as it turns, swings down the temperate coast of Alaska and gradually disappears. These two great currents and their inclosed eddies are far broader and less distinct than those of the North and South Atlantic, but they follow the same laws.
In a similar but lesser way the Indian Ocean has a strong westerly stream flowing straight across from Australia to South Africa, which is of immense help to ships returning from the East around the Cape of Good Hope. From Mozambique the water turns northward to make the return round, but here it is complicated by the peculiar conditions made by the inflow and outflow of the Red Sea, Arabian Gulf, and so on, and by the disturbing influences of the monsoons, until it can hardly be defined.
Of all these currents none is as well marked as the Gulf Stream. Its blue water is in such contrast to the darker, greenish hue of the remainder of the ocean that sailors can often tell when they enter the edge of the current, half their vessel being in and half out of the stream. If you approach from the west you find that the water at first shows a warmth of only fifty or sixty degrees near the surface; but as you sail on, this increases until, opposite Sandy Hook, you may get as high a reading on the thermometer as eighty degrees, and opposite Florida above one hundred degrees. This difference in temperature between the eastern and western margins of the Gulf Stream is owing to the presence of the great river of Arctic water flowing in an opposite direction between the Gulf Stream and the shore. Off Florida the Gulf Stream is about sixty miles wide; off New York it is over one hundred miles in width, but is less sharply defined. Its depth is hard to determine, but certainly amounts to several hundred feet. It is worth remembering that, although some guesses had been made at it before, Dr. Benjamin Franklin was the first man to study the Gulf Stream and to tell us anything of its origin and course.
The way in which some of these ocean currents affect the weather of the lands upon which they border shows how great is the influence of the sea upon land-climates; indeed, it may be truthfully said that only the continents and such great islands as Australia or Madagascar have any climate essentially distinct from that of the ocean in their quarter of the globe. But the equability that would reign over an ocean of quiet water, determining the amount of cold and heat by regular gradation in latitude between the equator and the poles, is completely upset by the great current-movements I have outlined. Scotland, for example, lies as far north as Labrador, and the latitude of London is above that of Lake Superior, yet neither have those terrible frosts and heavy snows which prevail in Canada, and make Labrador a land of ice almost uninhabitable. This difference is due almost wholly to the fact that the Gulf Stream pours its warm flood against the coast of Great Britain, and even tempers the Norwegian coast, keeps Barentz’s Sea largely free from summer ice, and clothes Spitzbergen with vegetation, although within ten degrees of the pole. Hence in the forests of northern Scandinavia Laps can dwell in much comfort on a line with the frozen barren grounds north of Hudson Bay.
A ROUGH NIGHT IN THE GULF STREAM.
On the other hand, the unfortunate coasts of Greenland are bathed in water chilled by months of captivity near the pole, and loaded with ice that cools down all the winds that blow ashore. Greenland itself is covered with an unbroken sheet of ice, hundreds or thousands of feet thick, yet most of it is no farther north than Sweden. The whole northeastern coast of America, down to Labrador, is incrusted with ice; and the region south of the St. Lawrence has a similar climate to Finland; while even farther south, Boston, within the protecting arm of Cape Cod, is in winter a city of frost and snow and fog from November till April, when it really is little farther north than sunny Naples, where one laughs at winter.
Similarly, in the Pacific Ocean, the northward movement of the great Japanese current makes the coast of China habitable and pleasant clear to the Sea of Okhotsk, gives the Aleutian archipelago a pretty decent climate, and causes the islands and coasts of Alaska and British Columbia to nourish the most magnificent forests in America, and to have a climate resembling that of Great Britain. Glasgow and Sitka are, in fact, in the same latitude, and under very similar climatic conditions, except that in Scotland there are no such lofty and cold mountains to precipitate constant rains as is the case along the northwestern margin of America.
Similar examples and contrasts might be drawn in other parts of the world. The weather in the interior of continents is pretty much alike on similar latitudes the world round, varying with height; but the climate of all sea-coasts is good or bad as a place to live, in accordance with the temperature of the water which the currents bring to that part of the ocean.
But the currents of the ocean influence something besides the weather. Upon them depends to a considerable extent whether a certain part of the coast shall have one or another kind of animals dwelling in the salt water. This is not so much true of fishes as it is of the mollusks or “shell-fish,” the worms that live in the mud of the tide-flats, the anemones, sea-urchins, starfish and little clinging people of the wet rocks, and of the jellyfishes, great and small, that swim about in the open sea.