USES OF SALT SEAS. 2I 
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 36°. 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 
3 Equator : 
g 90° 75" 60° 45° 30° 15° Bar 15° 30° 445° 60° 75° 90° 
Pole? +40° Pole 
Water at a Constant Temperatwre of 4° Cent. 
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? Itis 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 
