FAULTS PRODUCE SPRINGS. 545 
situations where it would he detrimental, are at 
the same time of the greatest service, in con- 
verting it to purposes of utility, by creating on 
the surface a series of Springs along the line of 
Fault, which often give notice of the Fracture that 
has taken place beneath. This important effect 
of Faults on the hydraulic machinery of the globe 
extends through stratified rocks of every for- 
mation. (See PI. 69. Fig. 2.) It is also pro- 
bable that most of the Springs, that issue from 
onstratified rocks, are kept in action through the 
instrumentality of the Faults by which they are 
intersected. 
A similar interruption of continuity in the 
masses of Primary rocks, and in the rocks of 
intermediate age between these and the Coal 
formation, is found to occur extensively in the 
Working of metallic veins. A vein is often cut off 
suddenly by a Fault, or fracture, crossing it trans- 
castle, on the wet side of the 90 fathom Dyke, and was so 
inundated with water that it was soon found necessary to abandon 
it. Another shaft was then begun on the dry side of the dyke, 
only a few yards from the former, and in this they descended 
'Uearly 200 fathoms without any impediment from water. 
Artificial dams are sometimes made in coal mines to per- 
iurm the office of the natural barriers which Dykes and Faults 
supply. A dam of this kind was lately made near Manchester, 
fy Mr. Hulton, to cut off water that descended from the upper 
•■ngion of porous strata, which dipped towards his excavations in 
u lower region of the same strata, the continuity of which was 
Ihiis artificially interrupted. 
G. 
N N 
