ingredients again, in the sea they would have to remain. There, accumulating in its waters, they would alter the quality of the brine, injure the health of its inhabitants, retard evaporation, change climates, and work endless mischief upon the fauna and the flora of both sea, earth, and air. But in the oceanic machinery all this is prevented by compensations the most beautiful, and adjustments the most exquisite. As in the atmosphere the plants are charged with the office of purifying the air by elaborating into vegetable tissue and fibre the impurities which the animals are continually casting into it, so also to the mollusks, to the madrepores, and insects of the sea, has been assigned the office of taking out of its waters and making solid again all this lixiviated matter as fast as the dripping streams and searching rains discharge it into the ocean.
47. Monuments of their industry.—As to the extent and magnitude of this endless task some idea may be formed from the coral islands, the marl beds, the shell banks, the chalk cliffs, and other marine deposits which deck the sea shore or strew the land.
48. Analysis of sea-water.—Fresh water is composed of oxygen and hydrogen gas in the proportion by weight of 1 to 8; and the principal ingredients which chemists, by treating small samples of sea-water in the laboratory, have found in a thousand grains, are—
Water....................... 962.0 grains
Chloride of Sodium........... 27.1 grains
Chloride of Magnesium......... 5.4 "
Chloride of Potassium......... 0.4 "
Bromide of Magnesia........... 0.1 "
Sulphate of Magnesia.......... 1.2 "
Sulphate of Lime.............. 0.8 "
Carbonate of Lime............. 0.1 "
Leaving a residuum of......... 2.9 " = 1000,
consisting of sulphuretted hydrogen gas, hydrochlorate of ammonia, etc., etc., in various quantities and proportions, according to the locality of the specimen.
49. Proportion of water to the mass of the earth.—If we imagine the whole mass of the earth to be divided into 1786 equal parts by weight, then the weight of all the water in the sea would, according to an estimate by Sir John Herschel, be equivalent to one of such parts. Such is the quantity, and such some of the qualities of that delightful fluid to which, in the laboratories and
