260 G - F - McEwen. 



coast in a few days if the depth does not exceed about 400 meters 

 (that is over the continental shelves). In the deep ocean, on the other 

 hand, particularly in the case of very broad currents, say 1000 or 

 more kilometers in width, the "mid water-current" may require several 

 months to become approximately fully developed 1 ). Thus the effect of 

 a wind is entirely different from what Zoppritz's theory shows, and 

 the time required for producing the effect is measured in days or 

 months, rather than in geological periods. 



IV. Qualitative applications of Ekman's theory to several peculiar 

 temperature distributions. 



Since, if the proceeding theory is true, it is possible for a wind 

 acting under proper conditions to bring bottom water to the surface, 

 and since we know from observations that the bottom water is cold, 

 abnormally low surface temperatures may be due, at least in some 

 cases, to a combination of circumstances which would produce an up- 

 welling of the cold deep water into the warmer surface water. 



H. Thorade (14) has compiled, from all reliable sources available, 

 a large amount of detailed information concerning the prevailing wind 

 directions and surface temperatures over the North Pacific Ocean cor- 

 responding to each month of the year (Figs. 20 and 21 are copies of 

 two of hi-; temperature charts, and they also indicate the prevailing 

 surface currents for the months of Jan. and Aug. respectively). He 

 assumes that the low temperatures near the coast are due to the up- 

 welling of cold bottom water, and points out a close correspondence 

 between the prevailing wind directions and the temperature distribu- 

 tion He does not give the velocity of the winds, but only the pre- 

 vailing directions, and devotes only one page to a qualitative applica- 

 tion of Ekman's theory, the results of which are shown to agree in 

 a general way with the observations on the seasonal distribution of 

 temperatures. This is the first application of the new theory of up- 

 welling to the California region. 



The statement made by Hoi way (9) that during the summer the 



*) The approximate value of the time required for such a current to attain 

 0,7 of its final value is given by the formula 



{ d xlsin*j 



ID sin * ' U J 



where (x) is the distance from the coast in kilometers across the stream and (d) and 

 (D) are depths in meters. 



