ORIGIN. The origin of mineral waters is often looked upon with much curiosity, and yet there is nothing unnatural about It. The rain water falling on the surface soaks down through the 'soil into the rocks and may slowly filter through them to a considerable depth, coining out to the surface at a lower level in the form of a spring; or again the water may reach sufficient depths to be subjected to great pressure or even heat, and coming to a fissure or being struck by an artesian-well boring. it will tend to escape to the surface through such an outlet. Many min eral springs are found along lines of faulting, since fault fissures afford a means of escape. The dissolved mineral substances no doubt are ob tained from the rocks through which the water has flowed. In some cases the waters in seeping through one type of rock may take up certain acids which later react on basic elements con tained in other rocks, thus producing salts. Most
waters contain some carbonic acid, which greatly increases their solvent powers in the presence of lime, magnesia, and iron; while if the waters are alkaline they may take up substances which are ordinarily rather insoluble, such as silica. The attacking power of the water may be still further increased if it is hot. There seems to lie some relation between hot springs and the geological structure of a region, as thermal springs are more abundant in areas where the rocks have been highly faulted or where there has heen volcanic activity in comparatively recent geological times. Mineral springs commonly con tain more dissolved material in regions of sedi mentary rock formation than in igneous or meta morphic areas.