SALINITY, GASES 55 



In order to obtain uniformity in the deter- 

 mination of chlorine (halogens) by different 

 workers, samples of " standard sea- water " are 

 now issued by the International Commission 

 for the Exploration of the Sea. 



Another method of determining the salinity 

 is based upon the fact that the refractivity of 

 water, i.e., the deflection undergone by a ray 

 of monochromatic light when passing from 

 air to water, stands in definite relation to 

 the salinity, and still another method is based 

 upon the measurement of the electrical 

 conductivity or resistance of sea-water, but 

 on the whole it may be said that the refrac- 

 tivity and conductivity methods of determining 

 salinity have not come into general use. 



Distribution of Salinity (see Plate III.). — 

 The factors affecting the variation in the 

 salinity of the surface waters of the ocean are 

 precipitation and evaporation, the inflow 

 of rivers, and the action of winds. In 

 general a high salinity is found in those regions 

 where the temperature and evaporation are 

 high and the rainfall is small, and vice versa ; 

 for instance the highest salinity occurs in 

 the eastern half of the Mediterranean and in 

 the northern half of the Red Sea, where the 

 salinity rises to over 39 per thousand — this 

 being a region of great evaporation and small 

 precipitation. The lowest salinities (under 



