256 G. F. McEwen. 



and his result is entirely different. But as was stated before, the 

 motion is not laminar, but is turbulent and the ordinary value of (p) 

 which gave the absurdly small value of (D) must be replaced by a 

 virtual value much greater than 0,014. The virtual value 



6. I* = 



would be different under different conditions of wind, velocity etc., and 

 can only be determined by current measurements and other observations 

 carried out under varying circumstances. From the rough measurements 

 now available 1 ), a mean value of (D) would be 75 meters. 



Experiments on the relative velocities of the wind and surface 

 current led to the following approximate relation: 



0,0127 , 

 7 ' V ' == /S^ V - 



where (V^) is the wind velocity and (V ) that of the surface water. 

 That is, at the latitude 45 the velocity (V ) of the surface water is 

 approximately 1 / 55 times that of the wind (V^) which causes it. This 

 multiplier would be about 0,013 at the poles, and would increase as 

 the equator is approached. If the wind velocity is in miles per hour 

 and the value of (V ) is required in meters per second the formula becomes 



8- V = V W . 



l/sm* 



From E km an' s theory, the time required for a steady current to 

 produce any fraction of the final limiting value is independent of the 



value of (ft) and the current would be practically fully developed in 

 24 "pendulum hours" 1 ). And thus outside of the tropics where this 

 theory does not hold, only a few hours are required to set up a 

 stationary state of motion, and the enormous times that Zoppritz 

 computed on the basis of laminar motion and the ordinary value of (fi) 

 are meaningless. 



Second typical problem. Assume as before an infinite ocean 

 of uniform depth (d), [(d) is greater than (D)] and of uniform density (q) 

 Suppose the surface to be inclined at a constant angle (d)). Solving as 

 before, the following results were obtained. The current will consist 



*) Ekman deduced the following approximate formula for deter- 

 mining (D). 



