38 



date, confused the calculations of the velocity, volume and 

 direction of the current that any given wind will set up in ahoal 

 water) and to make sure that all the pertinent factors have been 

 given due weight in the eouations. Known methods of estimating 

 the effect of a coastline 'in the direction of a wind driven current 

 account for some of these apparent discrepancies, but others rei^ain 

 to be explained. 



Wlien we turn to the chief problem of the wind as a motive^ force 

 i.e., how far the great Trans-oceanic drifts under the trade v/ind 

 belts, and around the Antarctic Ocean, are, in fact, kept in aotion 

 by the wind, or in what proportion wind friction combines here with 

 internal hydrostatics, we find few data at hand for quantitative 

 treatment. 



In these and similar cases, theoretic discussion of physical 

 potentialities can provide a series of accurately solved type 

 problems. And while the conditions to which such apply are far 

 simpler than prevail in nature, the basis for synthesis that they 

 afford corresponds to the actual state closely enough to meet 

 present needs for the critical examination of test cases, 



3. Penetration of Light 



Light is so important in the vegetable and animal econony 

 of the sea that the biologist constantly turns to the physicist for 

 information as to the depth to which light- rays of different .-jave- 

 lengths penetrate into the water, with intensity great enough to 

 serve plants in their photosynthesis, or to govern animals in their 

 tropisms, and in their metabolism. The theoretic coefficient of 

 absorption of light by pure water has been measured many times, vrnat 

 is now needed is empiric tests of what does actually happen in the 

 sea, at different localities, v;ith the sun standing at different 

 heights above the horizon, and under the widely differing condi- 

 tions of turbid.ity that actually prevail. In this, as in other 

 phases, the stage of quantitative measurement has been reached some 

 time since; the next rational step is the accumulation of data ever 

 the widest possible range of latitudes, locations relative to the 

 coastline, varying abundance of suspended silt or Plankton, different 

 seasons of the year, etc. 



0. CHEMICAL ASPECTS OF OCE^'^NOGRAPHY 



The studies of the Physical-Chemistry of sea v/ater that are now 

 in progress, like those of its physics, chiefly aim at enlarging our 

 factual knowledge of regional variations and our understanding of 

 events that take place in the cycle of matter there, rather than at 

 clarifying the nature of chemical processes as such. They thus bear 

 to the science of physical-chemistry as a whole a relationship more 

 subsidiary than do oceanic biology or physiology to current attempts 

 to fathom the riddle of life. We may also remark that a line should 

 be drawn between problems in the sea. that involve analysis of the 

 chemical reactions that actually take place there, and those which 

 include chemistry only in so far as it is necessary to determine the 

 amounts of one substance, or another, in the solution or in tne 

 sediments that clothe the ocean bottom, as adjuncts to other 

 problems. The first of these categories falls truly v/ithin tho 



