25 



are keot icy cold. 



Cold currents are also responsible for the drifts of ice fron 

 the Antarctic and Arctic to melt in lov/er latitudes, ^.vith all that 

 this entails as to sea chilling, effects on terrestrial climates, 

 etc., ;7hile this same melting process produces circulatory effects 

 in the nearby waters that have been the subject of much dispute. It 

 is, therefore, impossible to understand the thermal problems in the 

 sea if v;e do not understand the phenomena and causes of its circula- 

 tion, and vice-versa; this applies equally to the problems of salin- 

 ity; likewise to the regional and bathic variations in the concentra- 

 tions of oxygen, and of the various solutes. Circulation, of one 

 kind or anj'cher, also plays an active part in the events of sulo- 

 marine geology, as it sorts and transports sediments, attacks shore 

 lines and slopes, maintains conditions approaching equilibriu.n with 

 regard to the alkalinity, etc., of the water, and so forth. 



In short, no argument is needed to justify the study of ocee.n 

 circulation from the geo-physical standpoint, for here v/e face an 

 earthly phenomenon of the first rank. Currents in the sea also 

 intrude constantly on the attention of oceanic biologists; partly 

 bocausj this would be true of anything that controls the temperaxure 

 of the water, but also as agencies important in the migrations and 

 dispersa.ls of a great variety of animals and plants. This phase is 

 of great concern to the student of the problems of the marine 

 fisheries. 



The mobility of the waters of the oceans (with their high 

 specific gravity) also concerns the biologist as making possible the 

 planktonic existence of many groups of animals and plants, while per- 

 mitting other categories of animals to lead a stationary existence 

 fixed to the bottom, where they depend on the waters to bring their 

 food to them, instead upon their own powers of locomotion to carry 

 them to their prey (Page 45), 



The knowledge of currents that is needed by the biologist calls, 

 furthermore, for examinations of special regions so detailed that we 

 commence to see the circulatory bases for vital economy in only ?. 

 few areas, all of them near land; the North, the Norwegian and the 

 Barents Seas, for instance; the Baltic; the I^editerranean; the Gulf 

 of Maine; the Gulf of St. Lawrence; the Californian and Japanese 

 coastal waters. 



Currents, like temperatures (Page 89), also bear directly on 

 human affairs via the disturbing effect that any sporadic departure 

 from the normal state must have on the temperature of the water, 

 hence on the te-Tperature and barometric pressure of the overlying 

 air, to be reflected in weather abnormalities over the neighboring 

 lands (Pago 90). We also think here of the importance of ocean 

 currants in navigation; not only as they assist or impede passing- 

 ships and as the relative directions of current and of wind affects 

 the heights and shapes of waves, but also as the agencies responsible 

 for the menace to the traffic lines by icebergs. 



In short, there is no field of study, of soa or of its con'ounts, 

 that is not immediately concerned with the circulation of the v/aoer. 



