418 SPRINGS CAUSED BY FAULTS. 



manner by perennial springs. Hence the numerous alter- 

 nations of porous beds with beds impenetrable to water, that 

 occur throughout the entire series of stratified rocks, pro- 

 duce effects of the highest consequence in the hydraulic con- 

 dition of the Earth, and maintain a universal system of na- 

 tural Reservoirs, from which water overflows incessantly in 

 the form of Springs, that carry with them fertility into the 

 adjacent valleys. (See PI. 67, fig. 1, S.) 



The dischai'ges of water from these reservoirs are much 

 facilitated, and increased in number, by the occurrence of 

 Faults or Fractures that intersect the strata.* 



There are two systems of Springs which have their origin 

 in Faults, the one supplied by water descending from the 

 higher regions of strata adjacent to a fault, by which it is 

 simply intercepted in its descent, and diverted to the surface 

 in the form of perennial springs; (see PI. 67, fig. 1, H.) the 

 other maintained by water ascending from below by Hydro- 

 static pressure, (as in Artesian Wells,) and derived from 

 strata, which at their contact with the fault, are often at a 

 great depth ; the water is conducted to this depth either by 

 percolation through pores and crevices, or by small subter- 

 raneous channels in these strata, from more elevated distant 

 regions whence it descends, until its progress is arrested 



• Mr. Townsend, in his Chapter on Springs, states, that there are six dis- 

 tinct systems of springs in the neighbourhood of Bath, wliich issue from as 

 many regular strata of subterraneous water, formed by fiUralion through 

 either sand or porous rocks, and placed each upon its subjacent bed of clay. 

 From these, one system of springs is produced by overflowing in the direction 

 tpwards which the strata are inclined, or have their dip,- whilst another sys- 

 tem results from the dislocation of the strata, and breaks out laterally through 

 the fractures by which they are intersected. 



It is stated by Mr. Hopkins, (Phil. Mag. Aug. 1834, p. 131,) that all 

 the great springs in the Limestone District of Derbyshire are found in 

 conjunction with great Faults, " I do not recollect (says he) a single ex- 

 ception to this rule, for I believe in every instance where I observed a 

 powerful spring, I had independent evidence of the existence of a great 

 fault," 



