National Geographic : 1939 Jul
THE NATIONAL GEOGRAPHIC MAGAZINE States. Its waters are deep blue in color and unusually transparent. In these two charac teristics it even outranks the Gulf Stream. A 6y2-foot disk, when lowered beneath its surface, was still visible at 217 feet. Eels which inhabit not only the rivers of Europe and America but small brooks and ponds on both sides of the Atlantic con verge on the Sargasso Sea each year to breed and then die. BROWN ARROWS SHOW PREVAILING WINDS Winds, once the most important factor in navigation, supplying the motive power for oceanic voyages, are shown on the map by brown arrows. Although supplanted by steam and motor, they are again of im mense importance, for they are the very breath of the related sciences of aviation and meteorology. Most constant of all winds are the trades, which blow for days and even weeks with no more than a slight variation in velocity or direction. The South Atlantic, along with the South Indian Ocean, is especially favored, for here the trade winds reach their greatest development. In still another way is the South Atlantic fortunate, for it is never invaded by tropical cyclonic storms. These storms originate only in the doldrums, north of the Equator, where the air is always hot and sultry and squalls are common place. Other regions of light and variable winds are the horse latitudes, or calms of Cancer and Capricorn, where, in contrast to the doldrums, the air is clear and fresh. MIGHTY RIVERS IN THE OCEAN The prevailing westerly winds of the Temperate Zones blow in the Southern Hemisphere with a constancy second only to that of the trade winds. They have given the name "roaring forties" to the latitudes where they most regularly exhibit their turbulent temperament. Ocean currents are shown on the map by blue arrows and of these the Gulf Stream is the most important. Like the other cur rents, it owes its origin principally to the winds. Breezes, through friction, set in motion the surface waters of the sea, and these in turn impart their motion to the next lower water layer, and so on until an ocean current is set up. On the direction and force of the pre vailing winds depend the strength and permanence of the currents. The Gulf Stream's velocity changes with the seasons along with the intensity of the trade winds, to which it is indebted for its origin. Of a deep indigo-blue color so that its juncture with other waters is plainly evi dent, the Gulf Stream in its swift flow to the north cools so little that it is vastly warmer than the waters through which it passes. Tempering the climate of the north as it does, it is often called the "heating apparatus" of western Europe. The Labrador Current flowing southward from Davis Strait passes along the Labra dor and Newfoundland coasts and then skirts the eastern shoulder of the Grand Banks, bringing with it the ice found in this region during certain months. It was here in latitude 41046 ' north, longitude 50014' west, that one of the greatest of all sea tragedies occurred, when the Titanic, largest ship then afloat, sank on her maiden voyage after striking an iceberg, April 14, 1912. This disaster led to the establishment of the International Ice Patrol. Conducted by the United States Coast Guard, its expenses are paid by 14 nations according to their shipping tonnage. ICEBERGS FROM GREENLAND AND ANTARCTICA Most of the North Atlantic bergs are launched by the glaciers of Greenland's west coast. In the south of Greenland a small but prolific glacier gives birth to the bluish-hued bergs so difficult to see at night. But these Arctic icebergs are completely eclipsed by the much larger Antarctic ones with their longer life span. The northern bergs are seldom older than two years, while the southern bergs sometimes reach an age of ten years. Shown by white shading in the blue tint, the "northern and southern limits of ice" exhibit some queer kinks. Most peculiar of these is the tongue of ice, south of Mar tin Vas and west of Tristan da Cunha, which is driven north from the Antarctic by the cold Cape Horn Current. Such a map shows vividly how far to the east South America lies as compared to North America, and this is emphasized by the time zones, depicted by white lines. The time difference between London and Rio de Janeiro is only three hours, com pared to five hours between London and New York. The west coast of South America is about as far east as Jackson ville, Florida.