196 CURRENTS OF THE SEA. 



that we do not perceive the ceaseless turning of 

 the earth from west to east, is because all the 

 bodies near each other, at any given spot, share 

 equally in the motion. However, the speed of the 

 movement is not the same under different parallels 

 of latitude, but is less and less from the equator to 

 the poles. Under the latitude of 60°, it amounts 

 to about seven hundred feet in a second, while at 

 the equator it is as much as fourteen hundred. If 

 therefore a body were to be suddenly transported 

 to the equator from the former latitude, retaining 

 the speed with which it had there been moving 

 round, it must lag behind the bodies, which it 

 found at the equator, and which have a rate of 

 fourteen hundred feet in a second ; and the same 

 effect would result to the observer as if this body 

 were travelling from east to west with a speed of 

 seven hundred feet in a second. If, on the con- 

 trary, any body moving with the speed due to the 

 equator were to be brought to any higher latitude, 

 it must outrun all other bodies there, in the direc- 

 tion from west to east. 



From tliis you will see that all the ocean-water 

 which flows from the poles to the equator must 

 gradually take up a direction of motion from east 

 to west, and that all water flowing from the equator 

 to the poles must take one from west to east. 



But differences of temperature are not the only 

 cause which give rise to currents in the sea. We 



