RIVER-WATER. This is generally much softer and better accommodated to economical purposes than spring water. For though rivers proceed originally from springs, yet, by their rapid motion, and by being exposed during a long course to the influence of the sun and air, the earthy and metallic salts which they contain are decomposed, the acid flies off, and the terrestrial parts precipitate to the bottom. Rivers are also rendered softer by the vast quantity of rain water, which, passing along the surface of the earth, is conveyed into their channels. But all rivers carry with them a great deal of mud and other impurities; and when they flow near large and populous towns, they become impregnated with a number of heterogeneous substances, in which state the water is certainly unfit for many purposes; yet, by remaining for some time at rest, all the feculencies subside, and the water becomes sufficiently pure for most of the common purposes of life. River-water may be rendered still purer by filtration through sand and gravel.