ROCKS OF THE NORTHERN HIGHLANDS. 405 



overlie of the gneiss. The same force which doubled the Assynt 

 series back upon itself could also have brought the gneiss over the 

 Assynt series. 



These sections not only add to the proof of inversion and over- 

 thrust, they show that, even putting inversion on one side, the 

 alleged evidence for a conformable succession breaks down. The 

 gneiss in the western escarpment forms the upper part of the cliff 

 continuously from north to south, lying in apparently regular beds. 

 But the underfying rocks are a confused mass of fragments, some 

 right side up, others upside down, but neither the normal nor the 

 inverted blocks being continuous for many hundred feet. This 

 enormous crushing probably took place while the Assynt series 

 was being folded back by the thrust of the Caledonian. 



Junction South of the Arnaboll Valley. — At the opening of this glen 

 on the south side, the Arnaboll gneiss rises in several small humps, 

 from which the Quartzite dips in various directions, as if tilted up 

 by the upheaval of the gneiss. The chief junction is well seen at 

 the top of the slope, a little notch separating the two groups. Some 

 schisty, rather rotten beds are in contact with the Quartzite ; and 

 the Caledonian forms a low scarp at the east side of the gap, which is 

 but a few yards wide. The gneiss is of a reddish colour, and it is 

 associated with some grey felspathic schist, the whole being 

 penetrated by granite veins. The dip of the gneiss is E.S.E. at 60°, 

 while the Quartzite dips W.KW. at 70°-80°. The quartzite is the 

 lowest of the group, the base being a thin band of conglomerate like 

 the basement seam in Glen Coul, and the grit bed occurring in its 

 usual place about 10 feet above. After some sharp contortion, the 

 beds plunge over to the west, as already described. The discordance 

 between the gneiss and the Quartzite is thus seen to be very well 

 marked. 



Following the basement quartzite on the strike to the south, we 

 find it gradually rises to the vertical, and then is folded back so as 

 seemingly to dip below the Caledonian, the conglomerate being still 

 in contact, and the grit-bed about 10 feet below the gneiss. The 

 process by which apparent conformity is produced is thus very 

 easily observed. This overthrow is in the lowest quartzite, and is 

 quite irrespective of the great overthrown fold farther west. Several 

 other small contortions also occur in the quartzite before it takes 

 its final plunge down to the loch. 



Further to the south the lowest quartzite is crushed out, the Anne- 

 lidian Quartzite, and that only in part, being in contact with the 

 Caledonian. 



Taking the same line, but turning our attention to the gneiss, we 

 observe still more striking proofs of want of conformity. The 

 Quartzite strikes steadily to S.S.W., while the strike of the gneiss 

 is between S.W. and W.S.W. The Quartzite is thus brought against 

 higher and higher beds of gneiss, till finally the Arnaboll type con- 

 tracts to a narrow wedge and disappears, and the Quartzite comes 

 up to the Hope series, with which it remains in contact for miles to 

 the south. 

 Q. J. G. S. tfo. 155. 2 g 



