OVERLYING ROCKS OP ROSS AND INVERNESS. 159 



bedded gneisses of the central areas of Ben Fyn, Mulart, &c. is 

 itself one of the strongest arguments which can be adduced in proof 

 of the high antiquity of these rocks. The advocates of progressive 

 metamorphism in this region have strenuously maintained that so 

 long as the beds retain their evenly bedded character foliation remains 

 feeble, and that they only become highly metamorphosed when they 

 undergo rapid plications and foldings. These rocks of Ben Fyn 

 therefore should, according to that view, show but a partial change, 

 whilst, as will be readily seen from the notes by Prof. Bonney and 

 Mr. T. Davies, it is proved that they are in a highly crystalline 

 condition. Other so-called eastern rocks, however, such as those 

 referred to in the neighbourhood of Loch Shiel, are as greatly 

 plicated as are any in the western areas. I have divided the 

 Archaean rocks on the map into three groups, viz. the Loch- 

 Maree. Loch-Shiel, and Ben-Fyn series ; these may be unconformable 

 to one another, though at present the evidence of this is not conclusive. 

 A fourth group, less altered probably than any of these, and some- 

 what in the condition of the Pebidian rocks of Wales, may also pos- 

 sibly be partially represented in some of these areas, as some frag- 

 ments which occur frequently in the Torridon sandstones and breccias 

 are more nearly allied to such a group than to any of the others 

 specially referred to in this paper. Fragments, however, which 

 can be identified with rocks belonging to each of the groups men- 

 tioned are found in the conglomerates and breccias along the west 

 coast ; and these show clearly that little or no alteration has taken 

 place in the crystalline condition of the underlying rocks since these 

 fragments were derived from them. The whole of the evidence 

 obtained from these examinations tends therefore to confirm the 

 views maintained in my former paper, that the crystalline schists of 

 these areas must all be of Pre-Cambrian age, and that they are not 

 the equivalents of the fossiliferous Silurian rocks of the southern 

 Highlands and of Wales. 



APPENDIX. 



Note on the Lithological Characters of a Series of Scotch Rocks 

 collected by Dr. H. Hicks, F.G.S. By Prof. T. G. Bonney, M.A., 

 F.R.S., Sec. G.S. 



In the following remarks it is not my intention to attempt an ex- 

 haustive analysis of the microscopic characters of the rock-specimens 

 which Dr. Hicks has been good enough to entrust to me for descrip- 

 tion. This seems to me hardly necessary after the full descriptions of 

 rocks, in many respects similar, which have already been published by 

 Mr. T. Davies* and by myself f. Hence, in order to avoid burden- 

 ing the pages of our Journal, I have, as far as possible, noticed in 



* Geol. Mag. dec. ii. vol. vii. pp. 103 &c. 

 t Quart. Journ. Greol. Soc. vol. xsxvi. p. 98. 



