USES OF SALT SEAS. 23 



it, was first suggested by the observations of Kotzebue, Admiral 

 Beechey, and Sir James C. Boss. "Its temperature, according to 

 Kotzebue, is thirty-six degrees Fahr., or four degrees Cent.; the 

 depth of this bed, of invariable and uniform temperature, is twelve 

 hundred fathoms at the Equator; thence it gradually rises to the 

 parallel of about fifty-six degrees north and south, when it crops out, 

 and there the temperature of the sea from top to bottom is conjectured 



PolJ 90 ' " 



Fig 4. Therma 1 Lines ot equa 1 Temperature. 



to be permanent at thirty-six degrees. The place of this outcrop, no 

 doubt, shifts with the seasons, vibrating north and south, after the 

 manner of the Calm belts. Proceeding onwards to the Frigid zones, 

 this aqueous stratum of an unchanging temperature dips again, and 

 continues to incline till it reaches the Poles, at the depth of seven 

 hundred and fifty fathoms ; so that on the equatorial side of the out- 

 crop the water above the isothermal floor is the warmer, 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 

 derives 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. 

 Why 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 

 thermal dilatation. It is the salts of the sea that assist the rays of 

 heat to penetrate its bosom." The circulation of the ocean is indis- 

 pensable to the distribution of temperature to the maintenance of 



