FAULTS. 



109 



Fig 255. 



of the parts of the soil is more elevated than the other, no matter 



whether the crack remains open or not. These effects are often 



observed, and it is presumed they are all produced by the same 



cause, namely, upheaval. The beds are then inclined in opposite 



directions (Jig- 257), and one of the 



parts is more elevated than that which 



is adjacent ; the junction is sometimes 



distinguished by subterraneous work, 



either subsequently filled with gravel, 



or a slight fissure, or at least by a 



surface of separation, the planes of 



Fig. 257. Fault. 



which are smooth, and sometimes polished or striated vertically, 

 showing a close crack and a rubbing of one part on the other. 

 This arrangement has been called/a^// (from the German fall, an 

 accident, /a//, or sinking), because one part is lower than the other; 

 faults are observed in every kind of soil, and present crests or 

 ridges extending over great spaces, nearly in a straight line, some- 

 times broken here and there, but the different parts preserve the 

 same direction. 



12. Besides showing themselves on the surface, faults are also 

 perceived under ground, by the disturbance they have caused in 

 beds or veins worked for the benefit of the arts. It is thus, for 

 example, in coal measures, the 

 same bed of coal a, ft, c (Jtg- 258), 

 is found so much deranged in its 

 position, that the miner, after 

 having worked on a part of its 

 direction, from d to c, for instance, 

 finds it suddenly end, and would ^%-258. Bed dislocated by /</ Its. 

 at once abandon all his labours, had not experience taught him that, 

 by followingr the fault, he will find the deposit either above or 

 below the point where it abruptly terminated. Sometimes theft 

 results from these disturbances serious mistakes for speculators, 



11. What is meant by a fault? How are faults produced '/ 



12. Do faults always show themselves on the surface ? 



