23 



When so much is yet to be learned about the state of the surface 

 of the sea, it is not surprising that much greater gaps remain to be 

 filled in our knowledge of the underlying viater. In fact, the only 

 considerable regions for which oceanographers can yet claia even an 

 outline-knovrledge of the normal seasonal cycle of salinity co.nbined 

 with temperature from surface down to bottom, are the parts of the 

 northeastern Atlantic with its marginal seas (Norwegian, North, 

 Baltic, and Mediterranean) that have been covered by the cruises of 

 the International Commissions (Page 138); a much smaller coastv/ise 

 sector off the east coast of North America between Cape Cod and 

 Labrador; Californian and Japanese coastal waters; and the Javan 

 and South China Sea 7/here records were obtained quarterly for the 

 period 1917-1930. Even for these regions we need a much closer 

 knowledge of the minor seasonal fluctuations with their causes, es- 

 pecially of the irregular annual transgressions of one or another 

 water-mass which often play a disturbing (even destructive) role in 

 the general economy of the sea. 



In the ocean basins, the exploration of the underlying waters 

 is much further advanced for temperature than it is for salinity, 

 the thermal state being established in its broad outlines^ So 

 rapidly, in fact, did it prove possible to learn the abyssal^ tem- 

 perature, once attention was focused thereon, that while Wyville 

 Thomson, as late as 1873, found it necessary to combat the view 

 that the whole ocean basin was filled with water of 4^ Centigrade, 

 ten years later the basic distribution of deep sea temperatures was 

 generally understood. So many deep sea tem.peratures have subse- 

 quently been obtained in the North and South Atlantic that the gen- 

 eral distribution, at different depths, can now be plotted with some 

 confidence for these oceans, though as yet nowhere in detail. 



But the general uniformity of the abyssal and mid-level temr- 

 peratures over wide expanses, with the slow rate at T:hich these 

 alter from season to season, or from year to year, is our only 

 present warrant for extending any generalization to the Pacific as 

 a whole. Although a large nximber of serial and of deep bottom read- 

 ings have accumulated from that ocean, most of them have been con- 

 centrated along the American seaboard; between California, the 

 Aleutian Islands and Japan; around the western margin from Japan to 

 Australia; between Australia, New Zealand and Samoa; thence to 

 Samoa; thence to Hawaii; around that group; and along scattered 

 profiles across the basins. The situation is no better for the 

 Indian Ocean, except for the marginal zones. 



Data so scattered allow only the roughest of regional plotting. 

 In short, the thermal charts of these oceans cannot reach even to the 

 elementary standard so far attained for the Atlantic until serial 

 records of their temperatures for all depths, surface to bottom, 

 have been obtained over a much wider range of well selected locali- 

 tieso And this minimal rocuirerient would give only a first 

 approximation to the completed picture that must be aimed at finally. 



The gaps ir, present knowledge of the salinity of the ocean 

 deeps are still m.ore serious than for temperature, partly because 

 only a fraction as many records have yet been obtained; partly 



