CHAPTER III 

 THE OCEAN FEEDING-GROUNDS 



I. The salinity and density of marine waters, in particular on the 

 fishing-grounds. II. Oceanic circulation The physiology of 

 the North Atlantic, the Gulf Stream, and the Wyville Thomson 

 ridge The physiology of the North Sea. III. The tidal cur- 

 rents of the Channel Vertical currents. IV. The physiology 

 of the African Atlantic. V. Plankton Composition and 

 physiology. VI. Its distribution arid functions in relation to 

 ocean currents. VII. The conditions of the formation of 

 plankton. VIII. Plankton as an accumulator of energy The 

 problem of the alimentation of marine species The cycle of 

 oceanic life The hygiene of the seas. 



IT is not enough to describe a city house by house, 

 stone by stone, if we wish to enable others to know all 

 about it ; we must explain its relations with the sur- 

 rounding country, its means of communication with the 

 neighbouring cities, and, finally, its means of subsistence. 

 This task is imposed upon the historian as upon the 

 oceanographer ; but for the second it is a little less 

 difficult, as it reduces itself to the study of the open sea. 



I 



The salinity of water is expressed by the total weight 

 (usually in grammes) of the solid matter dissolved in 

 1,000 grammes, &c., of water. The salts dissolved are 

 chlorides, sulphates, bromides, and carbonates. Density 

 is the mean weight in grammes of a cubic centimetre 



70 



