132 LIGHT SCIENCE FOR LEISURE HOURS. 



process resembling suction is continually taking place 

 over the whole area of the equatorial Atlantic, the 

 agent being the intense heat of the tropical sun. No 

 one can doubt that this agent is one of adequate power. 

 Indeed, the winds, conceived by Franklin to be the 

 primary cause of the Atlantic currents, are in reality 

 due to the merest fraction of the energy inherent in 

 the sun's heat. 



We have other evidence that the indraught is from 

 below in the comparative coldness of the equatorial 

 current. The Grulf Stream is warm by comparison 

 with the surrounding waters, but the equatorial current 

 is cooler than the tropical seas. According to Professor 

 Ansted, the southern portion of the equatorial current, 

 as it flows past Brazil, ' is everywhere a cold current, 

 generally from four to six degrees below the adjacent 

 ocean.' 



If we here recognise the mainspring of the Grulf 

 Stream mechanism, or rather of the whole system of 

 oceanic circulation for the movements observed in the 

 Atlantic have their exact counterpart in the Pacific 

 we shall have no difficulty in accounting for all the 

 motions which that mechanism exhibits. We need no 

 longer look upon the Gulf Stream as the rebound of the 

 equatorial current from the shores of North America. 

 Knowing that there is an underflow towards the 

 equator, we see that there must be a surface-flow 

 towards the Poles. And this flow must as inevitably 

 result in an easterly motion as the underflow towards 

 the equator results in a westerly motion. We have, 



