^34 THE PHYSICAL GEOGKAPHY OF THE SEA. 



CHAPTER X. 



§ 461-499. — THE SALTS OF THE SEA. 



461. The brine of the ocean is the ley of the earth (§ 43). 

 The brine of the From it the sea derives dynamical power, and its 

 *^^^^°- currents their main strength. Hence, to understand 

 the dynamics of the ocean, it is necessary to study the effects 

 of its salts upon the equilibrium of its waters ; wherefore this 

 chapter is added to assist in the elucidation of what has already 

 been said concerning the currents and other phenomena of the 

 sea. Why was 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 which have been described in 

 a previous chapter (IX.). It is the salts of the sea that assist the 

 rays of heat to penetrate its bosom ;^ but for these, the solar ray, 

 instead of heating large masses of water like the Gulf Stream, 

 would play only at or near the surface, raising the temperature of 

 the waters there, like the sand in desert places, to an inordinate 

 degree. The salts of the sea invest it with adaptations which it 

 could not possess were its waters fresh. Were they fresh, they 

 would attain their maximum density at 39°.5 instead of 25°.6, 

 and the sea then would not have dynamical force enough to put 

 the Gulf Stream in motion, nor could it regulate those climates 

 we call marine. 



462. Were the sea fresh and not salt, Ireland would never 

 Were the sea of fresh havc presented thosc ever-green shores which have 

 uater— ^^qj^ f^j. ]jqj, ^]^q name of " Emerald ;" and the 



climate of England would have vied with Labrador for inhospi- 

 tality. Had not the sea been salt, the torrid zone would have 

 been hotter and the frigid colder for lack of aqueous circula- 

 tion ; had the sea not been salt, intertropical seas would have been 

 at a constant temperature higher than blood heat, and the polar 

 oceans would have been sealed up in everlasting fetters of ice, 



* Melloni has shown that the power of salt water to transmit heat is very much 

 ;;reater than that of fresh. 



