OVERLYING ROCKS OF LOCH MAREE. 817 



Putting aside the theoretical grounds which seem to me alone 

 sufficiently conclusive, that Silurian beds could not by any force indi- 

 cated here be converted into true gneiss and hornblende schists at 

 one point and be left unaltered at a lower horizon, we have here, 

 in my opinion, undoubted stratigraphical evidence which it seems 

 to me impossible to refute or to account for in any other way than 

 that of true discordancy by unconformity. 



That Prof. Nicol and the older geologists were therefore right 

 when they maintained that the Central Highlands contained and 

 were largely made up of some of the oldest rocks in Scotland, there 

 can, I think, be no doubt; but they have included with these rocks, 

 according to my view, a series of sediments belonging to a far more 

 recent period. On the other hand, Sir B. Murchison and Prof. 

 Geikie, who were the first to point out the presence of some at 

 least of these newer rocks, extended them into many regions oc- 

 cupied only by the older rocks. 



Though I was unable to examine any of the other areas under 

 dispute, I feel confident that the explanation offered in this section 

 at Glyn Docherty will hold true in those also, and that the meta- 

 morphic rocks of the Central Highlands will all prove to be of pre- 

 Cambrian date, the Cambrian and Silurian beds being contained in 

 basins or depressions only formed by the older rocks, generally un- 

 altered, and comparatively very limited in their distribution over 

 those areas. The great metamorphic areas here, as in all other 

 districts in Britain that I have been able to examine, are undoubt- 

 edly of pre-Cambrian date, and the changes which these rocks have 

 undergone seem to have been seldom if ever repeated since to any 

 important extent, whatever the forces at work at that time may 

 have been. 



Discussion-. 



Mr. He Eance asked whether the rocks of Ben Fyn were litholo- 

 gically similar to those of the western country, and whether the 

 former might not be intermediate in age. He doubted whether the 

 curve shown in the section of the stratified rocks in Glyn Laggan 

 could have been formed by the intrusion of granite there represented, 

 and asked what had become of their prolongation. 



Prof. Ramsay stated that he had been with Sir Roderick Murchi- 

 son over the country with which this paper was mainly concerned, 

 and had concurred with him in his view of the Lower Silurian age 

 of the gneiss of the Central Highlands. He had never seen an un- 

 conformity such as was represented in the section on the wall, and 

 did not see how the overlying rocks could have been deposited. The 

 strata near Loch Maree he had not examined ; others, however, in 

 whom he had confidence, had done so; but he saw no reason, seeing 

 how capricious metamorphic action was, why the Central Highlands 

 should not be metamorphosed Lower Silurian. He even believed some 

 of the granites themselves were only metamorphic. There is often 

 no sudden break between a comparatively unmetamorphosed and a 



Q. J. G. S. No. 136. 3 1 



