i8 



DOMESTIC WATER SUPPLIES FOR THE FARM 



are hard. In some springs the waters are exceedingly clear, the 

 bottoms being distinctly visible at a depth of many feet, but in 

 others the waters are muddy after severe storms. When clear it 

 is probable that the waters feeding the underground stream 

 reached it by percolation through the porous earth or rock, during 

 which its impurities were largely removed. Where muddy the 

 waters in part appear to have penetrated downward through 

 sinks or to have entered the rock directly as streams; in either 

 case they are very liable to pollution by impurities washed in with 

 the water. 



Tubular springs are most commonly of the gravity type, the 

 channels generally sloping from higher to lower levels. In both 

 drift and limestone, however, there are numerous exceptional 

 springs whose channels are at some points in their courses con- 

 siderably lower than their outlets. Under such conditions the 

 water may be under considerable artesian pressure in the lower 

 parts of its channel or even at its outlet. 



Fissure Springs. The term fissure spring is here used rather 

 comprehensively to include the springs issuing along bedding, 



FIG. 7. Fissure spring (artesian type). 



joint, cleavage or fault planes. (See Fig. 7.) The distinguishing 

 feature is a break in the rocks along which the waters can pass, it 

 being immaterial whether any considerable open space exists. 

 These springs differ from tubular springs in that they are as a 

 class of deeper-seated origin, as is attested by their temperatures. 

 The waters are almost never subjected to contamination, though 

 in many springs they are highly mineralized. Springs of this class 

 are often distributed along straight lines for considerable distances, 

 their position being determined by lines of fracture or jointing. 



