34 FAULTS. 



while in nature such joints are usually more uneven 

 and often most irregular. 



Another kind of compound fault is due to numerous 

 master joints in proximity, running more or less 

 parallel to one another, and all being concerned 

 more or less in forming the faulted ground ; or the 

 joints 'may branch off from one another, and after- 

 wards join again into one, as represented in the ac- 

 companying section and plan (figs. 20, 21, PL IY.) 

 The displacements may be tolerably equal along each 

 joint-line, thus forming what has been called a step- 

 fault (fig. 21). The movements, however, are often 

 most irregular, especially among the metamorphic 

 rocks. Long strips of country are sometimes met 

 with, occupied by " fault-rock," or strata so jumbled 

 up and mixed together, that it is nearly impossible 

 to separate one kind from another ; or, as is not 

 uncommon, the hard varieties of rock have crushed 

 up those that were softer, and masses of the first 

 will be enveloped in the debris of the others. 



Such a tract of faulted country was observed in 

 West Galway, extending from Dogs' Bay on the south, 

 northward past Clifden to Cleggan Bay. This 

 broken ground is sometimes more than a quarter 

 of a mile wide, while in places it is represented by 

 a dyke of fault-rock only a few yards in thickness. 

 This is altogether due to the disposition of the 

 lines along which the different movements have 



