12 PHYSICAL GEOGRAPHY OF THE SEA. 



with the exception of certain enclosed seas of limited extent, 

 is everywhere the same. The accurate measurements of Cora- 

 boeuf and Delcros show no perceptible difference between the 

 level of the Channel and that of the Mediterranean. In the 

 course of the operations for measuring the meridian in France, 

 M. Delambre calculated the height of Eodez above the level 

 of the Mediterranean at Barcelona, and its height above the ocean 

 which washes the foot of the tower of Dunkirk, and found the 

 difference to be equal to a fraction of a yard. 



The measurements which, at Humboldt's suggestion, General 

 Bolivar caused to be executed by Messrs. Lloyd and Filmore, 

 prove that the Pacific is, at the utmost, only a few feet higher 

 than the Caribbean Sea, and even that the relative height of the 

 two seas changes with the tides. 



The long and narrow inlet of the Bed Sea, which, according 

 co former measurements, was said to be twenty-four or thirty 

 feet higher than the Mediterranean seems, from more recent and 

 accurate investigations, to be of the same level, and thus to 

 form no exception to the general rule. 



The salts contained in sea water, and to which it owes its peculiar 

 bitter and unpleasant taste, form about three and a half per cent, 

 of its weight, and consist principally of common table salt(chloride 

 of sodium), and the sulphates and carbonates of magnesia and 

 lime. But, besides these chief ingredients, there is scarcely a 

 single elementary body of which traces are not to be found in 

 that universal solvent. Wilson has pointed out fluoric combina- 

 tions in sea water, and Malaguti and Durocher (Annales de 

 Chimie, 1851) detected lead, copper, and silver in its composi- 

 tion. Tons of this precious metal are dissolved in the vast 

 volume of the ocean, and it contains arsenic sufficient to poison 

 every living thing. 



Animal mucus, the product of numberless creatures, is mixed 

 up with the sea water, and it constantly absorbs carbonic acid 

 and atmospheric air, which are as indispensable to the marine 

 animals and plants as to the denizens of the atmospheric 

 ocean. 



In inclosed seas, communicating with the ocean only by 

 narrow straits, the quantity of saline particles varies from that 



