Page:Popular Science Monthly Volume 26.djvu/547

Rh matters in suspension, and the green ones are slightly charged with such substances. The solid particles held in the water constitute a multitude of infinitely little mirrors, from the outside of which is reflected the light that penetrates the mass of the liquid. The rays which are sent out, after having traversed only a thin stratum of water, preserve their yellow parts. If the reflections are attenuated, the water appears green; and if, on account of the absence of solid matter, they do not exist at all, the sea is of a deep blue. In an indigo sea, the crests of the waves will appear green on account of their lack of thickness. The same rules are applicable to fresh water; for the salt is almost without effect on the color of sea-water—not quite without effect, for, according to M. Spring, the clayey particles which make the waves yellow are precipitated with a rapidity proportioned to the salinity of the sea. These general laws are liable to be disturbed by numerous accidental circumstances or local causes. The presence of sea-weed, or of microscopic animalcules, may have great influence on the color of the water. In tolerably shallow basins, the color of the bottom has its effect.

Several seas or gulfs have been given names alluding to their colors. Some of these terms can be explained without difficulty, but others are not so easy to comprehend. The White Sea is so called on account of its ice, the Black Sea from its storms, and the Yellow Sea from the muddy waters poured into it by the Chinese rivers. The waves of the Vermilion Sea, near California, are colored by the Rio Colorado, which itself has a characteristic name. The water that washes the European coasts has no perceptible odor; or, if in single cases it may be odorous, the smell is due to mud, or to decomposing organic matters contained it it. Drinking-water, which is stored for some time may also acquire a smell which it had not at first, through the decay of the impurities in it. The cork of bottles containing salt-water is sometimes eaten by sulphuretted hydrogen formed in the water.

Sea-water owes its characteristic taste to the chloride of sodium held in solution, and to the bitter salts of magnesia which it contains. Sometimes organic remains or weak proportions of fatty matters become mixed with the superficial strata, so as to make them more nauseous than the same water drawn from greater depths. The pleasant taste of the water inclosed in oyster-shells is due to the savory animal juices that are dissolved in it. Mussels, which live and are fished near the shore, sometimes absorb impurities from the drift-matter around them, from which they develop the poisonous alkaloids called ptomaïnes; hence they are unhealthy at some seasons.

By a scientific prejudice that ruled for a considerable time, the bitter taste of sea-water was believed to be caused by traces of bitumen. The chemists who made analyses consoled themselves for not finding a sign of that substance, the existence of which they suspected, by