200 



University of California Publications. 



[Vol. 6 



'-n V„ or Yzq of the surface velocity. Following is a diagram 

 of the wind-velocity and of the water velocity at several depths: 



W//vr> 1/e.locitv 



The depth at which the velocity is V, and the angle with V a 

 is a, depends on the wind-velocity, the friction, and the latitude. 



By combining certain formulae developed in the theory, the 

 following relation can also be obtained: 



D = 7^ where D is the depth in meters and h is the 



1 sin # 



. , , . . meters _ „ . . , 



wmd-velocity in and A is a constant or approximately so 



seconds 

 as shown by the theory. By actually finding D, the depth at 

 which the current is reversed in direction, and by measuring /(, 

 the value of K can be found from the formula. It is also pos- 

 sible to find the constants in the more fundamental formulae 

 from which the above was derived, and then K can be computed 

 from them. However, in all cases certain of the variables in the 

 formulae must be actually observed before the constants can be 

 found. 



At the depth D at which the direction of the velocity has 

 changed so that it is exactly opposite to that of the wind, its 

 magnitude is only one-twentieth of the surface velocity. D. the 



