The New Student's Reference Work/Water
Wa′ter (H2O) is a clear, transparent liquid, formed of oxygen and hydrogen. It is almost colorless, though in large masses it looks blue. It freezes at 32°F. and boils at 212°F., and passes off in steam. Water dissolves almost everything it comes in contact with, so that strictly pure water is never found. Rainwater is the purest form, but even that has absorbed air and ammonia. Water is found very widely distributed in nature in the form of ice and snow, in watery vapor in the air, in lakes, rivers and seas, in the soil and rocks, in the sap and juices of plants and in the blood and flesh of animals. It covers three fourths of the surface of the earth, and forms a large part of the bodies of animals. The ocean is nature's great reservoir or cistern, and from it all other water may be said to be taken. A constant stream of vapor passes into the atmosphere and is condensed in colder regions, returning to the earth in the form of rain, dew, frost and snow, which fertilize the earth, are collected into pools, springs, lakes and rivers, and finally find their way back to the ocean. These waters all take up various substances, as is seen by the color of different rivers, which varies as the soil through which they pass. The water of the ocean is salt, but the saline or salty matter does not form a vapor, and so is left behind when the watery vapor rises from its surface. Besides its use in watering the earth and in feeding animal and vegetable life, water has been the great agent in forming the surface of the earth. A river carries with it a large amount of earthy matter, of which it has robbed the hills in which it springs, and deposits it in the valleys through which it flows; the great bars and deltas at the mouths of rivers being examples of the amount of land sometimes formed by the sediment in a river. This double process of breaking down and dissolving the rocks and of depositing and building up the land is constantly going on, and has been going on for ages. Geology gives the results of this constant action of water in past ages, as seen in the strata or layers of rocks which form the earth. In the form of ice or glaciers water has also had a large part to play in forming the continents. Some of the many purposes it serves are its use in supplying a motive-power to machinery, either mechanically, as in waterfalls, or by its expansion into steam, its use in cleansing and cooking or domestic purposes, its use in the laboratory as a solvent or dis-solver of most substances and its universal use by men, animals and plants for drinking purposes. Consult Tyndall's Forms of Water. See Glaciers, Ice, Ocean, Sea, Waterfall and Waterworks.