THE SPECIFIC GRAVITY OF THE SEA, ETC. 21i> 



velocity. How much, if to any extent, the former warm climates 

 of the British. Islands and Northern Asia may be due to sncii 

 a warm covering of the sea, may perhaps, at some future time, bo 

 considered worthy of special inquiry. We have already seen 

 (§ 434) that there is something else besides temperature that is 

 at work in effecting changes in the specific gravity of sea water. 

 Whatever increases or diminishes its saltness, increases or 

 diminishes its specific gravity ; and the agents that are at work in 

 the sea doing this are sea shells, the rivers, and the rains, as 

 well as the winds. Between 35" or 40° and the equator evapora- 

 tion is in excess of precipitation ; at any rate, there is but little 

 precipitation except under the equatorial cloud-ring (see Storm 

 and Rain Chart, Plate XIII.); and though, as we approach the 

 equator on either side from these parallels, the solar ray warms 

 and expands the surface water of the sea, the winds, by the 

 vapour they carry off and the salt they leave behind, prevent it 

 from making that water lighter. 



438. Nicely adjusted. — Thus two antagonistic forces are un- 

 masked, and, being unmasked, we discover in them a most ex- 

 quisite adjustment — a compensation — by which the dynamical 

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

 counterbalance each other; by which the climates of inter- 

 tropical 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 song 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-stalks of 

 plants (§ 303), but how much more exquisite is the system of 

 counterpoises and adjustments 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 vapour, 

 are all in such nice adjustment the one with the other, that there 

 is the most perfect compensation. By it they make music in the 

 sea, and the harmony that comes pealing thence, though not of so 

 lofty a strain, is nevertheless, like the songs of the stars, divine. * 



439. A thermal tide. — Suppose there were no winds to suck up 

 fresh water from the brine of the ocean ; 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. 



