472 WATER SUPPLY AND SEWAGE DISPOSAL 



ance with the behavior of the divining rod seldom failed to bare 

 water. 



We have already seen that every well which extends below 

 the water table is certain to contain some water and that the 

 efficiency of the well depends upon its tapping a bed, or pocket, 

 of loose, porous soil through which water may percolate read- 

 ily. Unless some reasonable connection can be shown to 

 exist between the divining rod and the bed of gravel buried deep 

 in the soil, "witching for water" must be classed with the out- 

 grown superstitions of the past. 



555. Deep Well Water. Wells are usually divided into two 

 classes, SURFACE WELLS and DEEP WELLS. In speaking of 

 wells as "surface wells" we do not mean that they are neces- 

 sarily shallow wells. We mean simply that they are fed by the 

 surface water, that is, by the ground-water near the surface of 

 the earth. In speaking of "deep wells" we mean that such 

 wells are fed from deep-seated veins of water. The water 

 which enters the surface wells has not usually passed through 

 much soil. It is water which has fallen as rain or snow near 

 the well; it has sunk into the ground, joined the ground-water, 

 and found its way more or less quickly into the well. 



The veins of deep-seated water, on the other hand, are sepa- 

 rated from the surface waters by layers of nearly impervious 

 clay or other material. Their source of supply is usually at 

 considerable distance from the well, often even hundreds of 

 miles. They are often ROCK WATERS, that is, water which has 

 collected in porous layers of rock, such as sandstone (wells 

 No. 2 and 4, Fig. 279). It is easily seen, therefore, that local 

 rains can make but little difference in the height of water in 

 deep wells. Most well water contains considerable mineral 

 matter in solution; this mineral matter produces a whitish, 

 curdy material when mixed with soap. Such water is called 



HARD WATER. 



656. Artesian Wells. By ARTESIAN WELLS we mean deep 

 wells. In most cases the water rises above the surface of the 

 ground. Such wells tap veins of water which usually, not only 



