OCEAN CURRENTS INFLUENCE OF THE EARTH'S ROTATION The student must bear in mind that the various move ments of the ocean which we have described, operate on a globe not a moment at rest, but rotating on its axis at the rate of over 1,000 miles an hour at the equator. Looking at the earth's axial rotation from west to east, and the deflec tion of the great equatorial currents to the west, a superficial observer would probably conclude that the latter are simply the results of the former. The earth's rotation, however, is not the cause of either marine or aerial currents, but simply modifies their direction, deflecting them from right to left in the Northern Hemisphere, and from left to right in the Southern. Now, the axial motion decreases from 1,000 miles an hour at the equator, or 500 miles under the 60th parallel—to nothing at the poles. If the earth were at rest, a current flowing from either pole towards the equator would proceed in a direct meridional direction. But it is not so, and as the higher latitudes have a less axial velocity, the velocity proper to high latitudes is less than that proper to lowlatitudes ; or in other words—a current starting with a low velocitAfrOm either pole towards the equator, cannot at once acquire the velocity proper to the lower latitudes which it traverses, and, consequently, falls behind, as it were, to the west A striking example of this is the Arctic current flowing into the Atlantic. The two branches
of this current combine off Cape Farewell, and the current gradually moves into latitudes having a higher axial motion, and is deflected to the west.
But a current flowing from the equator to either pole advances gradually into regions having a less velocity of rotation ;—the result is, that instead of falling behind the meridian, its higher initial velocity is so much greater than that proper to the higher latitude, that it advances before the meridian, and thus is deflected to the east. Currents generated in north tropical seas are generally deflected to the east—e.g., the Gulf Stream and the Japanese current—while those from the polar seas incline to the west ; and thus the cnrrents which impinge on the western coasts of both the Old and New Worlds are warm, while those which flow towards the eastern coasts are cold. Hence the average temperature of maritime countries on the western coasts of the continents is higher than that of other countries in the same latitudes on the eastern coasts. Thus the British seas and inlets are perfectly open all the year round, while on the opposite coasts of North America the St. Lawrence is ice-bound dur ing the winter.