CHAPTER IV. 



COMPOSITION AND PHYSICAL CHARACTERS OF THE HYDRO- 

 SPHERE. 



COMPOSITION OF THE HYDROSPHERE. 



The hydrosphere is never pure HoO, but ahvays includes dis- 

 solved salts and gases. The former are most abundant in sea wa- 

 ter and in the waters of salt lakes, the latter in some underground 

 waters. The composition of the larger divisions of the hydrosphere, 

 the oceans and the intracontinental seas, the lakes, rivers and 

 ground water, will be considered in turn. The totality of dissolved 

 salts constitutes the salinity of the water, though in the open sea 

 less than 80 per cent, of this is common salt (NaCl). The totality 

 of mineral matter is determined in parts (by weight) per 1,000 

 parts of water, or the number of grams in 1,000 grams (i liter) of 

 water. This amount is expressed as so many permille (Voo) of 

 salts. Thus a salinity of 35 permille exists when each 1,000 grams 

 (or approximately each liter) of sea water contain 35 grams of 

 salts, as in average ocean water. (For details and corrections of 

 method see Kvun\me\-2o: 221-222.) 



I. Salinity of the Sea. 



The salinity of the sea as a whole has been calculated at 34.49 

 permille, but that of individual divisions varies greatly. The fol- 

 lowing table adapted from Kriimmel gives the mean surface salinity 

 for the principal divisions, to which is added the mean salinity of 

 the entire volume. (Kriimmel-20 : jjj, 5(5/.) 



The seven important elements which form most of the salts con- 

 tained in solution in the sea water are: Chlorine (CI), Bromine 

 (Br), Sulphur (S), Potassium (K), Sodium (Na), Calcium (Ca), 

 and Magnesium (Mg). 



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