AND THE FORMATION OF VALLEYS. 105 



From this valley, near Lough Atorick, there seems 

 to be a branch fault running toward the east, north 

 of the hill called Tullymore, past Drummin and 

 Boleymore, into the bog bounding Lough Derg at 

 Spa Island. This fault could not positively be proved, 

 but it seems to shift the rock N.W. of Oghilly 

 House considerably towards the east, while the 

 wells near the shore of Lough Derg are probably 

 due to it. 



The fourth of these valleys extends from Lough 

 Cooter, along the Owendalulleegh River, to Marble 

 Hill. In this a fault has been traced from Lough 

 Cooter to near Marble Hill. We have called this 

 The Derrybrien fault, as it seems to have its greatest 

 throw in Derrybrien valley, immediately south of the 

 hamlet called Derrylaur, eight miles east of Gort, 

 where it brings down the limestone against the 

 Silurians. In the same valley, at Chevy Chase, 

 five miles S.E. of Gort, its throw is also consider- 

 able, as there the limestone is now in juxtaposition 

 either with the Silurian or the basal beds of the Old 

 Red sandstone. 



A fifth valley extends across the mountain group 

 north of the summit called Cashlaundrumlahan, with 

 which a fault is connected. We find in the Owena- 

 glanna River valley Lower Limestone shale, whose 

 south outcrop could not anywhere be found ; these 

 rocks probably are bounded on the south by the S.W. 



