Water. (Fn., Eau ; GER., Wasser,) In an article on Beverages, water claims to occupy a prominent position, both on account of its own importance as a common drink, and by reason of its forming the basis of numerous others. Besides, though water for drinking purposes is not manufactured or prepared, it is nevertheless an article of commerce, since it must be purchased by its consumers from the water companies which collect and supply it, and paid for in much the same way as any other article of food or of daily consumption. For this reason, also, it could not properly he omitted from the list of commercial beverages.
The primary source of water is the sea ; but all fresh water reaches us through the medium of the clouds, which are water in a state of vapour suspended in the atmosphere. A gigantic process of distillation is continually going on, owing to the evaporation of the water of seas, rivers, lakes, &c., by the heat of the sun. The vapour of water thus formed is recondensed by contact with a colder atmosphere above, and falls back to the earth in the form of rain, snow, and hail. In this way, the earth is furnished with a constant supply of water distilled from the ocean by the agency of the sun and the natural heat of the earth. As it falls through the atmosphere, rain absorbs a considerable quantity of the free gases existing in it, and hence becomes aerated with oxygen, nitrogen, and carbonic acid in varying proportions. Rain water is a powerful solvent, and therefore always contains more or less matter in solution, together with small quantities of dust which float about in dry air and are washed down by the first portions of the rain. Besides the free gases of which the atmosphere is composed, there are many gaseous impurities present, of which traces are invariably found in rain water ; these, however, are generally in such minute quantities that, if free from suspended matter, rain water may be practically considered as pure. If it is caught iu basins or tanks, and stored for any length of time, especially with exposure to the air, it soon becomes foul and impure by the introduction of foreign matter containing seeds or germs, too minute to be visible, but capable, under the influence of light and heat, of loading the water with myriads of living organisms, which die and become putrid. In this state, water is wholly unfit for drinking purposes, and it must be carefully filtered before using. Rain water, owing to the absence of saline matters, is more favourable to the production and development of these organisms than water obtained from rivers, brooks, aud springs, and should therefore never be used after long exposure to the air. Soft water, containing carbonic acid gas, exerts–a solvent action upon lead ; hence tanks and pipes of these metals should never be employed. The insipid character of rain
water and its liability to develop organic life render it unsuitable for general use as a beverage.
The water in lakes and ponds which are not supplied by running streams is rain water caught and retained in natural depressions of the earth, or in valleys closed at the lower end by some obstacle. Here it comes into contact with the soil and with vegetable matter, and becomes charged with organic impurities; these, however, are not injurious to health unless they are permitted to become putrid. The vegetable life so abundant in most lakes and ponds of large size gives off much carbonic acid gas, which is retained in solution in the water. and this gas renders it much brisker and fresher to the taste than ordinary rain water. That the water of ponds is better fitted than any other for drinking purposes is clearly shown by the fact that the instinct of cattle leads them to prefer it to running water, or to rain water caught in tubs, and that they are more healthy when they have access to the former kind.
Rain water which falls in hilly districts and on the sides of mountains collects in streams and brooks, of greater or less size ; these gradually unite, forming rivers. In such waters, the impurities are often visible to the eye. It is frequently of a red colour as it flows through rocks of red marl, which contain much oxide of iron in their composition ; it becomes rnilky in colour as it descends from the glaciers of Iceland or the slopes of the Andes, owing to the fine white sand which it takes up in its comse. Many of our English rivers are grey or brown in colour; they are brown when running through a peaty or boggy country ; and when the quantity of suspended vegetable matter is excessive, they are sometimes quite black to the eye. Only when perfectly clear, is the blue colour natural to large masses of water distinctly perceptible. But among the rocky and other materials with which water comes in contact in and upon the earth, there are many which it can dissolve, and the presence of which cannot be detected by the sense of sight. Hence, the elearest and brightest of waters—those of springs and transparent rivers—are never chemically pure, even when filtered; they all contain in solution a greater or less quantity of saline matter. sometimes so table shows the amount in grains pet gallon of solid mineral matter contained in the waters of some important lakea and rivers:— Lime in combination with carbonic and aulphurie acid is the most common impurity in stream and river water ; and it is to this substance and to magneaia that such water owea the property termed " hardneae," or that of curdling with soap. Pure watera are alwaya soft; and from this quality the absence may be inferred of any large proportion of lime and magnesia aalts.