§438,439. THE SPECIFIC GRAVITY OF THE SEA, ETC. 217 



the sea, the winds, bj the vapor they carry off and the salt they 

 leave behind, prevent it from making that water lighter. 



438. Thus two antagonistic forces are unmasked, and, being 

 Nicely adjusted, unmaskcd, wc discovcr in them a most exquisite 



adjustment — a compensation — by which the dynamical forces 

 that reside in the sunbeam and the trade-wind are made to coun- 

 terbalance each other ; by which the climates of intertropical seas 

 are regulated ; and by which the set, force, and volume of oceanic 

 currents are measured. This compensation is most beautiful ; it 

 explains the paradox (§ 434), gives volume to the harmonies of 

 the sea, and makes them louder in their songs of Almighty praise 

 than the noise of many waters. Philosophers have admired the 

 relations between the size of the earth, the force of gravity, and 

 the strength of fibre in the flower-stalk of plants (§ 303), but how 

 much more exquisite is the system of counterpoises and adjust- 

 ments here presented between the sea and its salts, the winds and 

 the heat of the sun ! The capacity of the sun to warm, of the 

 sea water to expand, the quantity of salts these contain, and the 

 power of the wind to suck up vapor, are all in such nice adjust- 

 ment the one with the other, that there is the most perfect compen- 

 sation. By it they make music in the sea, and the harmony that 

 comes pealing thence, though not of so lofty a strain, is never- 

 theless, like the song of the stars, divine. 



439. Suppose there were no winds to suck up fresh water from 

 A thermal tide, thc brluc of the occau ; that its average depth were 



3000 fathoms; that the solar ray were endowed with power to 

 penetrate with its heat from the top to the bottom ; and that, from 

 bottom to top, the seas of each hemisphere, in thermal alternation 

 with the seasons, were raised to summer heat and lowered to win- 

 ter temperature : the change of sea level from summer to winter, 

 and from winter to summer, in one hemisphere, would, from this 

 cause alone, be upward of 125 feet ; and in its rise and fall we 

 should have, from pole to pole, the ebb and flow of a great ther- 

 mal tide that would turn with the sun in the ecliptic, and tell the 

 seasons by the march on the tide staff of its rising and falling 

 waters. But difference of level would not be all that would give 

 strength and volume to this tide ; difference of specific gravity 

 would lend its weight as so much dynamical force, which differ- 

 ence would create an upper and under annual tide from one 



