170 Mr. R. Griffith on Mr. Weaver's Paper relative 



published by me as extending southward from Crotty's rock in 

 the Monavoullagh mountains to Lismore, we find exactly the 

 same suite interposed between the conglomerate base and the 

 carboniferous limestone of the valley of the river Blackwater. 



It is true, that the distance between Crotty's rock and Lis- 

 more, is greater than between Gloundolgan and Knockna- 

 granny, in section No. 2, or between Bally voil Head and 

 Ballyvoil bridge, in section No. 1 ; but it will be observed 

 by referring to the plan, that the conglomerate and red slate 

 at the coast dip to the south at an angle of 70 ; while at 

 Gloundolgan, four miles west of Ballyvoil Head, they dip 

 south at an angle of 45 ; further to the westward the dip is 

 south at an angle of 15; and as we approach the summit of 

 the Monavoullagh mountains at Crotty's rock, the strata effect 

 a nearly horizontal position. Owing to this circumstance, 

 though the section is complete at Ballyvoil Head in the hori- 

 zontal distance of one mile and a half, yet between Crotty's 

 rock and Lismore the same suite occupies a horizontal di- 

 stance of eighteen miles. 



Having stated these facts, I think it unnecessary to do 

 more than observe that Mr. Weaver's argument in proof of 

 the impossibility of the red slate and conglomerate at Crotty's 

 rock composing a part of the same series with the red slate 

 and conglomerate of Ballyvoil Head, namely, the nearly hori- 

 zontal position of the one, and the highly inclined angle of the 

 strata of the other, is untenable ; and I confess I am surprised 

 at such an argument being used, as every practical geologist 

 must be aware of its weakness. 



The northern part of Mr. Weaver's section between the 

 Suire and the Blackwater does not take the same line as mine, 

 as his crosses over the Knockmildown mountains, and mine 

 over the Monavoullagh range situated to the east ; but to en- 

 able me to test the accuracy of his section, I have made one 

 nearly in the same line. (See section, No. 3. in the plate.) If 

 we compare this section with Mr. Weaver's, nothing can be 

 more dissimilar. Mr. Weaver's section represents a base of 

 graywacke slate, which supports unconformably a cap of old 

 red sandstone ; but according to my section, it is evident that 

 e entire mountain range belongs to the old red sandstone 

 series. The anticlinal axis is exposed to view in the valley of 

 the river Ownashad, at Corrignagour, three miles north of 

 Lismore : it consists of alternations of dark-red slate and dark- 

 red quartzose rock, the slate predominating. These strata 

 are succeeded both on the north and south sides of the axis 

 by beds of brownish-red quartz-rock, red sandstone, and red 

 clayslate, occasionally associated with fine-grained conglome- 

 rate, a thin bed of which appears at the surface on the south 



