[/S£S OF SALT SEAS. 21 



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

 Kotzebue, is 36'' Fahr., or 4° Centigrade; the depth of this 

 bed, of invariable and uniform temperature, is 1,200 fathoms at the 

 Equator ; thence it gradually rises to the parallel of about 56^ north 

 and south, when it crops out, and there the temperature of the sea 

 from top to bottom is conjectured to be permanent at ^6". 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 750 fathoms; so that on the equatorial side of 



Ecru a. tor 



Q 



jj» 



/^QO" 75' 60° 45' 30° 15° 15" 30* 45° 60' 75' 90"J 

 PoleT I I -^^^'i ! I I 1 ; 1 -■^40°, I 7Pol 



le 



Fig. 4. — Thermal Lines of equal Temperature. 



the outcrop 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 

 the meteorological and climatic conditions which rule the develop- 

 ment of life ; and this circulation could not exist — -at least, the 



