THE NATURAL DRINK OF MAN. Water constitutes the natural drink of man. No other liquid can supply its place. Its presence, however, in the body is not permanent. It is discharged from the body in different ways; by the urine, the feces, the breath, and the perspiration. In the first two, it is in a liquid form, in the others in a vaporous form. It is estimated that about forty-eight per cent. is discharged in the liquid, and fifty-two per cent. in the vaporous form; but the absolute as well as the relative amount discharged depends upon a variety of circumstances. Water is never found perfectly pure, since it holds in solution more or less of almost every substance with, which it comes in contact. Rain falling in the country remote from habitations is the purest water that nature furnishes, for it is then only charged with the natural gases of the atmosphere. In cities it absorbs organic and gaseous impurities, as it falls through the air, and flowing over roofs of houses carries with it soot and dust. Water from melted snow is purer than rain-water, since it descends in a solid form, and is therefore incapable of absorbing gases. Rain-water is not adapted to drinking purposes, unless well filtered. All water, except that which has been distilled, contains air, and it is due to this fact, that aquatic animals can live in it; for example, put a fish in distilled water and it will soon die. MINERAL IMPURITIES. Rain-water, which has filtered through the soil and strata of the earth, dissolves the soluble materials, and carries them down to lower levels, until they finally collect in the sea. Common well, spring, and mineral waters contain from 5 to 60 grains to the gallon; sea-water contains 2,000 grains while in some parts of the Dead Sea there are 20,000 grams to the gallon. The principal mineral impurities of well and spring water are lime, magnesia, soda, and oxide of iron, combined with carbonic and sulphuric acids, forming carbonates, sulphates, and chloride of sodium, or common salt. The most general, however, are carbonate and sulphate of lime.