CURRENTS AND STREAMS 29 



water on the surface of a revolving grind- 

 stone slips backward on the surface of the 

 stone instead of travelling along with it. 



If there were no land masses in its path the 

 water of the oceans would all move round and 

 round over the surface of the earth, while at 

 the same time flowing slowly north and south 

 from the equator, but as the earth moves 

 faster near the equator than at the poles the 

 motion from east to west would vary accord- 

 ing to the distance from the equator. Thus, 

 at the equator, the earth moves practically one 

 hundred and seventy-five miles a minute 

 while in temperate latitudes it moves only 

 about one hundred and thirty-five miles a min- 

 ute and at the poles it moves far slower. As 

 the currents of water moving north or south 

 reach portions of the earth's surface which 

 are moving slowly and as this water, when it 

 left the equator, was moving rapidly towards 

 the east, it has a tendency to travel faster than 

 the earth itself, thus forming a current from 

 west to east. The cold water from the north 

 and south,"fcoming from portions of the earth 

 which are revolving slowly and reaching re- 



