of the circulation of the Atlantic. Any other assumption of the 

 level of no motion would lead to unreasonable and contradictory 

 results about the vertical structure of the Atlantic circulation. 

 The same hypothesis was applied to a dynamical analysis of the 

 Black Sea circulation by the author (194-2,1943). In this case 

 the results could be checked against other techniques in deter- 

 mining the level of no motion, and the computed dynamical structure 

 of the Black Sea was in good agreement with the observed conditions. 



Defant's results for the Atlantic Ocean are shown in figure 1. 

 The depth of the "zero layer" (D) increases with increasing lati- 

 tude, both, on the Northern and on the Southern Hemisphere, In the 

 North Atlantic, the depth of the zero layer is more irregular than 

 in the South Atlantic, which has its analogy in the more compli- 

 cated current pattern of the North Atlantic. 



Based on the chart shown in figure 1, zonal averages of the 

 depth of no motion (D) were computed for the North Atlantic, and 

 plotted against the latitude in figure 2. For the South Atlantic, 

 individual values were used as given along the meridian of 20°W, 

 since the variation of D in the east-west direction is small com- 

 pared with the variation of D in the meridional direction. The 

 values of D, according to A. Defant's chart, are indicated in figure 

 2 by circles, whereas the curve represents the function D = -K sincp. 

 The constant K is different on the Northern and Southern Hemisphere, 

 but the variation of D with latitude follows this law closely. It 

 is seen that the zonal averages of the depth of the layer of no 

 motion in the North Atlantic, and the corresponding depths along 

 20°W in the South Atlantic, can be represented very closely by 



D(qO = -K sincp, (12) 



13 



