146 DE. H. HICKS ON THE METAMOEPHIC AND 



culty of tracing the floor in the area now to be described is also 

 greatly increased in consequence of the very highly faulted condition 

 of much of the ground. If we begin the section with Ben Eay, we 

 shall find that the Torridon Sandstone, which forms the base of this 

 picturesque mountain, rests towards the north-west on a floor of 

 the old gneiss, but at a much lower horizon than it does at Ben 

 Slioch on the north side of the lake. 



The Torridon Sandstone in both cases is alike in its general 

 characters. It is occasionally brecciated, though much less so than 

 in the mountains still further west, about Gairloch. For the most 

 part it shows well-rounded fragments along this line and as far as 

 the shores of Loch Torridon. Here and there shaly bands are 

 found ; and on the north shore of Loch Torridon I found these 

 occurring almost to the base of the series. The colour of the sand- 

 stone varies from a bright pinkish and reddish colour to a dark 

 green. The former is due to the felspar present, and to a reddish 

 coating of the quartz ; and the latter to a fine chloritic material 

 disseminated through the rock, and also coating the quartz grains. 

 Indications are abundantly present in the sandstones and breccias 

 of the kinds of rocks which must have yielded the materials ; and 

 it is abundantly clear that they must have differed considerably at 

 the time in their degree of crystallization. For instance, at Gairloch 

 the fragments may be readily matched with the rocks on the upturned 

 edges of which they now repose. In the Torridon area the evidences 

 are clear that similar rocks were being denuded, as well as some 

 chloritic rocks and some less altered slaty beds. That fragments 

 of these less altered rocks occur here in combination with those 

 of the true gneiss rocks is clear proof that there were some Pre- 

 Cambrian rocks in these areas, as in Wales, which had not under- 

 gone a great change before the Cambrian rocks were deposited upon 

 them. These comparatively unaltered rocks in Wales have not, as 

 shown by the fragments in the conglomerates, undergone much 

 change since that time, though they have been depressed to great 

 depths and have suffered repeated crushings and other effects of 

 local disturbances. The finding in these areas, as in Wales, of frag- 

 ments of highly crystalline rocks with those so much less altered is 

 most interesting, and should lead us to be careful in placing any of 

 the even moderately altered rocks in the newer series, unless the 

 evidence of their geological position is beyond the possibility of 

 doubt. 



We see therefore from the fragments in the conglomerates and 

 sandstones in these areas that some comparatively but slightly altered 

 rocks were being denuded by the Cambrian seas ; hence we must be 

 prepared to meet with these somewhere. Possibly this fact may have 

 a more important bearing on the supposed evidence of progressive 

 metamorphism in these areas than we are able at present to realize. 



In this area there seems to be clear evidence that the quartzite 

 series was deposited unconformably on the Torridon Sandstone. In 

 the quartzite series are some subordinate bands of a yellowish calca- 

 reous shale. These are theso-called fucoidal bands, found here and 



