62 THE OCEAN. 



polar oceans. But the waters wliicli flow from the north and south 

 are always in excess, in consequence of the continual impulse of 

 the trade- wind ; and wlien they arrive in tropical latitudes they are 

 influenced by a new current, the true cause of which is the rotation 

 of the earth on its axis. In fact, owing to the incoherence of its 

 particles, the ocean does not obey in an absolute manner the rotatory 

 motion of the earth, which carries it from west to east. In descend- 

 ing from the poles to the equator, and thus crossing latitudes 

 whose speed of rotation is greater than their own, they are constantly 

 drawn obliquely towards the west, and this continual retardation 

 of their motion behind that of the rotation of the globe becomes, 

 in relation to the surface of the sea, an apparent motion from east to 

 west. Upon their meeting in the tropics, the polar currents, being 

 both affected by a side movement, strike each other obliquely, then 

 re-unite in the same oceanic river, and flow directly towards the 

 west in the opposite direction to that of the solid earth. It is thus 

 that the equatorial^ current is produced, which with the two polar 

 currents determines all the movements of the waters in each oceanic 

 basin. The other rivers of the sea are simply branches from them, 

 caused by the form of the continents. 



The equatorial current, which is a continuation of the polar currents 

 and forms with them a vast semi-circle, cannot be freely developed 

 around the circumference of the globe. Arrested in the Atlantic by 

 the American continent, in the Pacific by Asia and the archipelago 

 which unites that continent with J^ew Holland, it breaks against the 

 shores and divides into two halves which flow back in the direction of 

 the poles, the one descending towards the south, the other ascending 

 to the north. The immense river thus returns to its source, but at the 

 same time the motion of terrestrial rotation, which at its outset caused 

 it incessantly to deviate towards the west, now urges it obliquely in 

 the opposite direction. Under the equator, the angular speed of the 

 terrestrial surface around the axis of the planet being much more con- 

 siderable than under any other latitude, the waters coming from the 

 tropics into temperate seas are animated by a more rapid movement 

 towards the east than those amidst which they flow. They deviate in 

 consequence in an easterly direction, and when the returning current 

 reaches the polar sea it seems to come from the west. Thus the grand 

 circuit of the waters is completed in each hemisphere. The Atlantic 

 and the Pacific have each their double circulatory system, formed of 

 two immense eddies united in the torrid zone by a common equatorial 

 current. As regards the Indian Ocean, being bounded on the north 



