PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 581 



increased, and now amounts to ten; at the 40th degree it is fifteen; 

 and when the current reaches Newfoundland, or the 45th degree 

 of north latitude, the difference is twenty. 



Here the current meets the grand banks, which are commonly 

 supposed to deflect it eastward; but when we know that it has 

 been acquiring more and more easting from the time that it left 

 the West Indies, and that it has now a surplus of it equal to 

 twenty ; when we further consider that its northerly force has 

 been, during the same time, diminishing — we caa readily under- 

 stand that it would move almost due east from Newfoundland to 

 the European coast, even if the grand banks did not exist. 



In proceeding from the 25th to the 45th degree the current is 

 impelled by two distinct forces, one of which acting alone would 

 have carried it due north, and the other acting alone would have 

 carried it due east. The northerly force is at its maximum w^hen 

 the current starts from the 25'th degree, and gradually diminishes 

 until it reaches the 45th degree,- when it is exhausted. The east- 

 erly force — the difference — is nothing at starting from the 25th 

 degree, but manifests itself immediately afterward, and gradually- 

 and continuously increases as long as the current runs northward. 

 When, at the 45th degree, the current ceases to run northward, it 

 is subject to the easterly force only. It can therefore only move 

 due east. While moving eastward it is continually growing cooler,, 

 and therefore has an increasing tendency to move toward the equa- 

 tor; in other words, it begins to move south-east, and continues in 

 that direction until the easting is exhausted. This happens near 

 the 25th degree of north latitude. The water of the current has 

 now become neutral, that is, it possesses no diflerence from the 

 w^ater of the earth in that latitude ; and therefore, as it continues 

 its course towards the equator, it flows south-west. When the 

 current reaches the equator it is in a condition analogous to that 

 in which it arrived at Newfoundland. It possesses a surplus of 

 -westerly force or westing, which may be represented by twenty. 

 The tendency to move south is gone, but the westing or difference 

 is at its maximum. In fact it has only a tendency to move rela- 

 tively westward; audit actually does move in that direction, from 

 the western point of Africa to the eastern point of South America.. 

 By this time the water has become so much heated that it over- 

 flows toward the north, that is, it moves north-west until it reaches 

 the Gulf of Mexico. Its westing being now gone, it becomes neu- 

 tral, that is, it possesses the same easterly velocity as the earth in 



