South East Trade wind region (10°S through 35°S) agree well with 

 Defant's values. The computed values D are plotted in the den- 

 sity section, figure 5? for comparison with the depth D in the 

 central parts of the South Atlantic according to figure 2. 



Probably, the estimated angles a are the most inaccurate. 

 However, the estimate of D by equation (22) should serve only to 

 check the order of magnitude of the factors involved in this pos- 

 sible mechanism of "mass compensation" to determine the level of 

 no motion. Another fact which must be kept in mind is that this 

 calculation only considers the meridional component of the ani- 

 sobaric mass transport. 



At this point, the dashed curve in figure 5 may at least be 

 mentioned briefly. It connects the maximum depth of the lines of 

 equal density ( 0%), and is in some way related to the tilting of 

 the axis of the subtropical gyre. This tilting in meridional 

 direction toward the poles with increasing depth has already been 

 mentioned by A. Defant (1941), but so far no explanation has been 

 given for this gross feature of the oceanic circulation. 



VIII. The coefficient of internal friction (r) 



In figure 6, M is the vector of the geostrophic mass trans- 

 port, and M is the vector of the true mass transport which is de- 

 flected by the angle a from the direction parallel to the isobars. 

 The difference vector, M - M , is in some way related to the average 



o 



internal friction in the whole water column from z = to z = -D. 



Assume horizontal, non-accelerated motion under the influence 



of internal friction. Then 



- ~ grad p+M xf+RrO, (23) 



P 



31 



