12 PILYSICAL 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 Rodez 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 Red 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. 
Thesalts contained insea 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 
