USES OF SALT SEAS. 
27 
° e permanent at thirty -six degrees. The place of this outcrop, no 
c 011 1) shifts with the seasons, vibrating north and south, after the 
manner of the Calm belts. Proceeding onwards to the Frigid zones, 
us aqueous stratum of an unchanging temperature dips again, and 
Pig. 4. 1 hevmal Linos of equal Temperature. 
continues to incline till it reaches the Poles at the depth of seven 
hundred and fifty iathoms ; so that on the equatorial side of the out- 
crop the water above the isothermal floor is the wanner, but in Polar 
seas the supernatant water is the colder.” 
In the saline properties of sea water Maury discovers one of the 
principal forces from which currents in the ocean proceed. “ The 
brine of the ocean is the ley of the earth,” he says ; “ from it the sea 
< erives dynamical powers, and its currents their main strength. 
Hence, to understand the dynamics of the ocean, it is necessary to 
study the effects of their saltness upon the equilibrium of the waves. 
W by is the sea made salt? It is the salts of the sea that impart to 
its waters those curious anomalies in the laws of freezing and of 
lermal ddatation. It is the salts of the sea that assist the rays of 
heat to penetrate its bosom” The circulation of the ooean is indis- 
pensable to the distribution of temperature-to the maintenance of 
the meteorological and climatic conditions which rule the develop- 
ment of life , and this circulation could not exist — at least, the 
character of its waters would he completely changed— if they were 
i'si in place of salt. “Let us imagine,” says M. Julien, “that 
6 8ea ’ now entirely composed of fresh water, of one uniform 
emperature from the Pole to the Equator, and from the surface to 
