Water is found in Nature in three states or conditions—as ice, vapor or steam, and as simple water. These three forms have the same chemical composition—the substance being a compound of oxygen and hydrogen, represented by the formula H2O; but the physical condition depends entirely on its temperature. Under ordinary atmospheric conditions water is a solid below 32 degrees Fahrenheit; a gas above 212 degrees Fahrenheit, and a liquid between these temperatures.
The purest form of water which exists in nature is rain water, though this always contains a little oxygen and carbon dioxide dissolved from the air. To obtain pure water artificially, any ordinary water is distilled, when all the solids dissolved in it are left behind. River water and spring water always contain a small quantity of solid matter, the amount and nature of the dissolved solids depending on the nature of the rocks over which the water has flowed.
Geographically it may be considered under the four heads of springs, rivers, lakes, and the ocean, which taken together forms the hydrosphere of the earth.
WHERE SPRINGS HAVE
THEIR SOURCE
Springs, or the natural fountains of water, take their rise from reservoirs stored under ground. Water maintains a level, and hence the height to which a spring will rise depends on that of the level from which it is supplied. If the internal reservoir be on a hill, and the spring should gush out in a valley, the water may rise to a considerable height and form a natural fountain; but, on the other hand, if the reservoir be at some depth below the surface, the water may never reach the surface, and mechanical aid may be required to obtain it.
These internal reservoirs are in a great measure supplied by moisture derived from rain, snow, mist, and dew. The atmospheric water enters the earth through porous rocks, or by means of fissures, and continues to sink until arrested in its progress by rocks, such as clay, which will not permit the water to pass, or by faults which check it from spreading. The waters will then gush forth as a spring, of greater or less size, according to the supplies it may have received.
HOW MINERAL SPRINGS
ARE FORMED
All springs contain a certain portion of air and gas, and also some solid matter, usually in the form of salts. When these salts are abundant, mineral springs are the result, which may be classified according to the character of their several properties, as acidulous, chalybeate, sulphurous, saline, calcareous, and silicious.
Acidulous or acid springs are those surcharged with carbonic acid gas.
Chalybeate springs are those in which iron, in the form of carbonate or sulphate, is held in solution.