On the Class ijicatio7i of the Granitic Rocks of Ireland. 311 



14. " On Terminal Curvature in the South-western Counties." 

 By W. A. E. Tssher, Esq., E.G.S., of H.M. Geological Survey. 



The author discussed the views advocated by Mr. D. Mackintosh 

 on the terminal curvature of slaty beds (Q. J. G. S. vol. xxiii. 

 p. 'S26), and objected to the hypothesis that the jDhenomenon was 

 produced by the action of ice in any form, which was the agency 

 to which Mr. Mackintosh was most inclined to ascribe it. The 

 author thought that what has been called terminal curvature might 

 be produced by three distinct causes, namely: — 1. The curvature 

 produced by internal movements at great depths, afterwards ren- 

 dered superficial by long subsequent denuding agencies ; 2. The 

 action of wedging frosts on the upturned edges of the beds, as ad- 

 vocated by Mr. Godwin -Austen ; and 3. The intrusion between the 

 laminte of the rocks of the roots and rootlets of growing trees. 



15. '^ On the Chronological Classification of the Granitic Hocks of 

 Ireland." By G. H. Xinahau, Esq., M.E.I.A. 



The author adopts Scheerer's definition that a granite is a rock 

 of certain constitution, in which all the constituents are separately 

 developed, and gives the name of elvanites to those granitic rocks in 

 which part of the constituents are not perfectly crystallized. The 

 elvanites pass into true granites on the one hand, and on the other 

 into plutonic or volcanic rocks. They are thus "passage-rocks" 

 between the two sections. 



The author apparently regards all granites as formed by the meta- 

 morphosis either of the sedimentary rocks in which they occur, or of 

 the plutonic rocks associated with these. Even intrusive granites 

 are the product of an extreme degree of metamorphosis. Of meta- 

 morphosis he distinguishes two kinds, namely : — Iletajpe-psis, or 

 regional metamorphosis, extending over larger or smaller areas, 

 and due to aqueo-igneous action ; and Paropiesis, or local meta- 

 morphosis, caused by heat generated at or near local igneous action 

 or a protrusion or sheet of igneous rock. 



The author then indicates the application of these principles to 

 the classification of the granitic rocks of Ireland in the chrono- 

 logical order of the sedimentary deposits with which they are asso- 

 ciated, and divides these rocks into 11 classes, corresponding to the 

 Cambrian, Cambro- Silurian, Silurian, Carboniferous, Triassic, and 

 Tertiary series, with five intermediate classes, the latter generally 

 divided again into subclasses. The granitic rocks of different 

 districts in Ireland are then described in some detail, and referred 

 to their places in the proposed chronological scheme. 



16. " The Cambrian Rocks of South-east Ireland." By G. H. 

 Kinahan, Esq., M.E.LA. 



The author states that these rocks are greatly altered by meta- 

 morphic action. Quartz rock occurs in dykes and other masses 

 among the Cambrian and Cambro-Silurian rocks, but chiefly among 

 the former ; it may be foliated and converted into quartzite by what 

 the author calls metapepsis (see preceding paper). 



Of tlie Cambro-Silurian rocks the base is seen only in two places — 



