PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 585 



I have remarked that the further a current moves northward the 

 further it must also move eastward. When this fact is reah'zed, it 

 becomes plain that the elliptical currents could not approach 

 nearer the poles than they do. A current starting from the 25th 

 degree of north latitude and impelled toward the north pole, 

 could not get within a thousand miles of that place before it 

 would be moving directly eastward, and as soon as it cooled it 

 ■would begin to move south-eastward. This easterly tendency of 

 the poleward currents render large polar interspaces inevitable. 



I have described the currents as if they move in straight lines 

 from point to point, but the truth is the}' must move in curves. 

 The current from the west neutral point in the northern hemi- 

 sphere begins by moving almost due north, then a little to east of 

 north, then more mid more eastci'ly, until at length the easting is 

 so great that the current moves due east. As it cools it begins to 

 turn a little to the south of east, then flows more and more south- 

 ward, until it ceases to move eastward at all, and for a very short 

 distance it moves almost due south. But soon it begins to turn a 

 little westward, then more and more westward, until at length it 

 moves due west. It now begins to be heated and to turn a little 

 northerly, then more and more northerly until it ceases to move 

 westward and has reached its neutral point. 



From this brief review it is plain that all the currents tend to 

 move in curved lines. We can now perceive the absurdity of the 

 idea, which is expressed in so many of our books, that the trade 

 winds cause the equatorial currents to move westerly. The fact 

 is that the equatorial currents generally move more westerly than 

 the trade winds do; and the elliptical currents on their polar side, 

 are more easterly than the winds that blow in the same latitude. 

 This could not be the case if the winds caused the currents. In 

 the Pacific, about ten degrees north of the equator, a counter cur- 

 rent runs easterly, while, on each side of it, the main currents run 

 west. If the currents here depend upon the winds blowing west- 

 ward — what produces the counter current which flows directly 

 against the wind ? It should be remarked that the wind only 

 afiects the ocean a few feet below the surface, whereas many of 

 the currents extend thousands of feet below. 



Local Cureents. 

 If two currents proceed from near the equator (or from any 

 lower latitude to a higher), one of which is local and the other a 



