224 Br. C. Callmcaij — Notes on Metamorphimi. 



an arkose of the gneiss, has suffered such intense crushing as to 

 resemble a grit for a thickness of several feet or yards. It is thus 

 very difficult to distinguish between the true grit and the smashed 

 Hebridean, even in good specimens of the two ; and it is of course 

 more difficult to determine where the one leaves off and the other 

 begins. 



Great pressure often produces an appearance of conformity between 

 rock-groups. In Glen Coul, for example, the Hebridean usually 

 strikes to the north-west at a high angle ; but, just when it is folded 

 over the dolomite of the Assynt series, the strike twists round 

 through 70° or 80°, and the old gneiss dips to the south-east in 

 perfect conformity with the undei'lying dolomite. A similar change 

 takes place up the glen, where the great squeeze has j^ushed or 

 folded the Caledonian gneiss over the quartzite. The Hebridean 

 maintains its normal strike until we reach the point where the newer 

 gneiss overhangs. Here the pressure has brought the strike round 

 into accordance with that of the overlying rocks, gneiss and quartzite. 



Few delusions have done more to retard the progress of our 

 science than the current hypotheses on metamorphism. It has been 

 taken for granted, even by those who claimed to be our geological 

 pastors and teachers, that the upper of two rock groups, conformable 

 or otherwise, must be the younger. Thus the Highland gneiss was 

 " proved " to be " Silurian." Yet no fact is more familiar than that 

 in mountain chains inversion is rather the rule than the exception. 

 Our recent work in the Highlands has demonstrated that the structure 

 of the country is in accordance with this principle. I have walked 

 on beds of rock Ij'ing fiat as they were deposited, and, without 

 removing my feet from them, have followed them yard by yard, till 

 I have stood on them, again lying flat, but upside-down. I have seen 

 these inverted strata bent into folds, in which, of course, the tops of 

 the anticlines were formed of the oldest beds. One da}', I climbed up 

 the south-western shoulder of Ben More of Assynt, and, at a height 

 of 2500 feet, found myself on vertical Hebridean gneiss, capped by 

 Jiorizontal conglomerate. Without leaving the bare rock, I descended 

 the slope a distance in vertical height of 1500 feet, and there saw 

 the gneiss lying flat upon the top of the conglomerate, the conglomerate 

 itself being turned bottom upwards. Many a weary mile have I 

 paced round the precipitous coast of Sutherland in the north of 

 Assynt, keeping always to the same ledge of quartzite, with steep 

 cliffs of gneiss rising on the inland side. Winding in and out of the 

 fiords, I ever saw the Hebridean reposing as uninterruptedly upon 

 the quartzite as if the " fundamental " gneiss were mere beds of 

 chalk overlying a band of greensand. Yet, climbing the cliffs and 

 striking inland for a mile or two, never leaving the gneiss, I found 

 it underlying the same quartzite, with its accompanying flags and 

 dolomite, just as in the escarpment I had left behind me. These are 

 not mere speculations ; but statements of facts which I saw as plainly 

 as I see the paper on which I write. It is by such proof as this that 

 the " conquest of the Highlands " is now challenged, and it remains 

 for the followers of Murchison to find a refutation, if they can. 



