102 THE RELATIONS BETWEEN FAULTS, OPEN JOINTS, 



they, and others that could not be worked out, pro- 

 bably belong to one system, and were formed simul- 

 taneously. Nos. 5 to 10 are connected with the 

 group of hills called Slieve Aughta, and the relations 

 between them and the features of the ground have 

 been carefully worked out, as will appear from the 

 following : 



In Slieve Aughta there is only one large north- 

 and-south val]ey, that of Lough Graney ; but the 

 east-and-west valleys are numerous, and lines of 

 fault have been proved to occur in each. The latter 

 valleys can be traced from the limestone country on 

 the west to the limestone country at Lough Derg, 

 while the faults could only be proved to have shifted 

 the beds in parts of them. 



The series of faults seen in this district are made 

 much clearer by the presence of different kinds 

 of rocks now in juxtaposition, although they were 

 originally several hundred feet asun.der; the dark- 

 blue limestone and the yellow and red Old Eed 

 rocks occurring on one side of the fault, while 

 the gray and green Silurian rocks are found on the 

 other. 



In places, some of what are here considered faults 

 might possibly only be Silurian cliffs, at the base of 

 which the Old Red sandstone and limestones were 

 deposited, as the rocks strike with the line of fault ; 

 this is more especially the case with the Cloonnagro 



