xiv INTRODUCTION 



ganisms and the water. Available data on vertical sections of temperature and salinity 

 for the different ocean basins, the basic data for the treatment of the dynamics of the 

 movements of the water masses, are presented in the section of this report following this 

 Introduction. There is also, on subsequent pages, a short statement on available tidal 

 records. The only information on biological data is contained in the catalogue of institu- 

 tions. It would have been desirable to catalogue the available data on oxygen content, 

 the minimum oxygen layer, and the COj-content of seawater, chemical relations largely 

 controlled by organic activity in conjunction with circulation, but to do so was im- 

 practicable. 



2. The study of the interaction of the sea and the atmosphere; solar radiation and its 

 penetration into seawater. Except to indicate data on temperature and salinity and to 

 catalogue institutions engaged on researches in marine meteorology, this complex of 

 subjects is not specially considered in this volume. Here may be noted only some geo- 

 physical and biological commonplaces. It is generally known that the engine that drives 

 the atmospheric and oceanic circulations is the Sun, and the engine that actuates life on 

 the earth, through its making photosynthesis possible, is the Sun. On the circulation of 

 the atmosphere and of the waters in the oceans, the rotation of the earth on its axis has a 

 directing influence. Any changes in density of seawater take place only at the sea surface 

 by heating or cooling, by precipitation or evaporation. Below the surface, the changes 

 are by the mixing of water masses of different densities. Winds blowing over the surface 

 of the sea produce surface currents which may uphold an abnormal distribution of density. 

 The characteristics of the contact zone between the atmosphere and the sea surface are of 

 great importance. Any change in the velocity of the wind over the surface results in a 

 change in the velocity of the surface currents. Since water possesses great heat capacity, 

 ocean currents cause the transfer of large quantities of heat. A change in the velocity of 

 an ocean current, due to a change in atmospheric circulation, may later influence meteoro- 

 logical conditions in a remote region. This concept may be of value in long range weather 

 forecasting, for one of the principles utilized in such forecasts is that of the time lag 

 between changes in oceanic phenomena and the corresponding change in atmospheric 

 conditions. Correlations of the kind indicated have been established in some parts of the 

 earth, as in western Norway. The depth of penetration of light into sea water controls 

 the depth to which plants may thrive in the sea. 



It would be desirable to present synopsis of information available on these topics, 

 but that could not be done for this report. 



3. The study of the ocean-bottom — its configuration, the material on its surface, 

 and the material that lies below it. The present state of knowledge of the configuration 

 of the sea-floor is indicated by five charts; notes are made on the latest studies of marine 

 bottom deposits; the results of studies of gravity at sea are contained in a chapter on that 

 subject; a summary of present knowledge of submarine earthquake epicenters is given on 

 three charts, there is a map showing the positions of the seismological stations of the world, 

 and there is a brief discussion of the structure of the ocean basin as indicated by seismo- 

 logical data, accompanied by a map of deep-focus earthquake epicenters; and finally there 

 is a chapter on the magnetic survey of the oceans. The summary discussions of these 

 aspects of the oceans are comprehensive and indicate how far knowledge of them has 

 advanced. 



