18 COMPOSITION OF THE SEA. 



sulphur, copper, silex, potash, chlorine, iodine, 

 bromine, ammonia, and silver. What a dose ! 

 Let bathers think of it next time they swallow a 

 gulp of sea water. 



Most of these substances, however, exist in com- 

 paratively small quantity in the sea, with the ex- 

 ception of muriate of soda, or common table salt; 

 of which, as all bathers know from bitter experience, 

 there is a very considerable quantity. The quantity 

 of silver contained in sea water is very small in- 

 deed. Nevertheless, small though it be, the ocean 

 is so immense, that, it has been calculated, if all 

 the silver in it were collected, it would form a 

 mass that would weigh about two hundred million 

 tons ! 



The salt of the ocean varies considerably in 

 different parts. Near the equator, the great heat 

 carries up a larger proportion of water by evapora- 

 tion than in the more temperate regions; and thus, 

 as salt is not removed by evaporation, the ocean in 

 the torrid zone is salter than in the temperate or 

 frigid zones. 



The salts of the sea, and other substances con- 

 tained in it, are conveyed thither by the fresh- water 

 streams that pour into it from all the continents 

 of the world. Maury, in his delightful work, " The 

 Physical Geography of the Sea," tells us that "water 

 is Nature's great carrier. With its currents it con- 

 veys heat away from the torrid zone, and ice from the 

 frigid ; or, bottling the caloric away in the vesicles 



