252 G- F - Me E wen. 



d) This cold water at or near the ocean bottom has a slow drift 

 agreeing in direction with the average direction of the surface drift, and 

 is driven to the surface on striking the slope of the continental shelf. 

 Local variations in the temperature of the cold coast water are due to 

 the submarine valleys and other irregularities in the slope of the con- 

 tinental shelf. 



6. A study of the proceeding investigations shows that the general 

 method employed was to first examine the data and then to formu- 

 late a hypothesis to account for the observed results, the hypothesis 

 being supported partly by the fact that it accounted in a qualitative 

 way for the particular observations used, and partly by the theory of 

 Zoppritz. Some writers used the effect of the earth's rotation and 

 others did not. Sometimes erroneous statements regarding the observed 

 facts were used in support of the explanation. The temperature distri- 

 bution was regarded as constant thruout the year. No quantitative 

 tests were attempted, and the explanations given by the different writers 

 are inconsistent with each other. So the question is still an open one. 



III. Hitman's theory of oceanic circulation. 



It is well known that the motion of large masses of water in the 

 ocean is accompanied by irregular vortex motions that cause the com- 

 putation of the actual frictional forces according to the methods of 

 rational hydrodynamics to be worthless. There is, in fact, an obvious 

 disagreement between the results of hydrodynamics on the one hand 

 and experience on the other. Therefore, for practical purposes we have 

 had to be satisfied with purely empirical formulae, which because of 

 their very limited field of application, have been unable to afford any 

 help to oceanography. But all of the factors affecting the motion of 

 ocean water can be taken into account if problems of a sufficiently 

 simple type are formulated. By devising a series of such simple typical 

 problems and solving them by exact analytical methods in which all 

 of the factors are used, a sort of framework can be formed about which 

 a theory of ocean currents corresponding to the different actual problems 

 can be built. The actual problems, however complex they may be, can 

 then be most readily attacked, not by analytical methods, but by 

 suitably combining the proper typical problems that have been solved. 



By proceeding in this way a number of very important results have 

 been obtained which are the immediate consequences of the general 



