﻿376 Beports and Proceedings — Geological Society. 



developed, and gives the name of ehanites 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 

 metamorphosis 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 

 metamorphosis he distinguishes two kinds, namely : — Iletapepsis, or 

 regional metamorphosis, extending over larger or smaller areas, and 

 due to aqueo-igneous action ; and Faroptesis, or local metamorphosis, 

 caused by heat generated at or near local igneous action or a pro- 

 trusion 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 eleven classes, corresponding to 

 the Cambrian, Cambro-Silurian, Silurian, Carboniferous, Triassic, 

 and Tertiary series, with five intermediate classes, the latter generally 

 divided again into sub-classes. The granitic rocks of diiferent 

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

 to their places in the proposed chronological scheme. 



16. "The Cambrian Eocks of South-East Ireland." By G-. H. 

 Kinahan, Esq., M.E.I.A. Communicated by Prof. Eamsay, F.E.S., 

 F.G.S. 



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 the Cambro-Silurian rocks the base is seen only in two places, 

 at Greenore and on the S.W. coast of Wexford. At the former it is 

 a fine reddish conglomerate, lying on or against schists; at the latter 

 a massive slate conglomerate. The rocks of this series in ascending 

 order are : — 1. Black carbonaceous shales and slates, or grey beds 

 with subordinate beds of grit ; 2. Green and grey grits, shales and 

 slates ; 3. The Ballymoney series of green, grey, black, and red 

 grits, sandstones, slates and shales, with interstratified igneous rocks; 

 ■i. Eed, purple, and green beds, usually more or less argillaceous. 



The Cambrian formation generally consists of green, purple, or 

 reddish grits, shales and slates, but here and there with grey or 

 even black beds. The author describes the Cambrian rocks in the 

 various areas in which they occur, namely, at 



Howth, where they are but little altered in the N., becoming more 

 altered towards the S. 



Bi'ay Head, generally unaltered, and containing many specimens 

 of Oldliamia, and with massive dykes of quartz rock. 



S.E. Wicklow, where the western boundary is doubtful. Near 

 Carrick mountain and to the westward the rocks are much altered, 



