where (eB and Cs may be either ‘constants or functions of X only. On 
the bottom Z= A we mst have 
ie = =O 
“4 u=Y=a hs 
beeause of the vertical friction. Along the coast which for the sake of 
simplicity may be supposed to be vertical 
} ) (5) 
because of horizontal friction. In the region very far from either coast 
or the wind region, we have 
A=oe ® Uh = Va A) 
let us define D and 1X ty 
, Ly = m/ Ar/Peose 3 ae me] frag : 
(7) 
D: 4s the "depth of frictional influence" defined by Ekman (1905) in his 
theory of wind-driven ocean currents, and D is a quantity having a die 
mension of length and may be called "frictional distance". This is a 
measure of the horizontal turbulence. 
If we put 
(8) 
