382 C. CALLAWAY ON THE OTEWER G-NEISSIC 



We conclude from these two traverses that vertical gneiss striking 

 to (roughly) N.N.E. gradually slews round to a north-westerly 

 direction, and in the same graduated manner falls in dip to 40°, 

 where it rests upon the conglomerate and grit. 



We have here observed the following facts : — 



(1) Eed and green grit, which rests on gneiss at Coniveall, is 

 overlain by the same gneiss (for there is no break in its continuity) 

 in the southern sections. 



(2) In Coniveall the grit terminates downwards in conglomerate, 

 but to the south the conglomerate is at the summit, in both cases 

 being in contact with the gneiss. 



(3) The vertical gneiss in the Ben More massif gradually changes 

 its strike and dip till it is seen to overlie the conglomerate. 



These appearances seem to me inexplicable except on the suppo- 

 sition of an overthrow of the gneiss and grit upon the dolomite. 

 But corroborative evidence may be adduced. 



/Section at the north end of Scounan More. — Scounan More*, 

 situated to the south-south-west of the last section on the opposite 

 (the west) side of the Oykel, is a mass of gneiss with nearly vertical 

 foliation, whose strike produced northward would coincide with the 

 strike of the gneiss in Ben More. The rock is of the usual coarse, 

 massive type, and is very distinctly foliated. At the north end the 

 ridge falls down abruptly on to the col (Bealach Choinnich) which 

 separates it from Brebag. This notch marks a fault, quartzite against 

 gneiss. The junction is well seen in the steep slope down to the Oykel, 

 a little south of the col. The gneiss dips S.E. at 70° ; and the 

 quartzite is in actual contact, dipping to S. 30° E. at 20° ; but at a 

 little distance the quartzite is nearly horizontal. I followed the 

 dislocation downwards for hundreds of feet, and as a stream kept 

 nearly to the fault, and washed the rock-surface clean of debris, 

 the evidence was singularly clear. The gneiss was a little contorted 

 at the junction, and rather decayed, besides being "messed" with 

 chloritic matter. The great discordance of dip was steadily main- 

 tained. 



Eeascending to the pass, we find its steep southern side occupied 

 by a dark-green shaly rock, passing upwards into a green gritf 

 (No. 95, p. 417) of the usual Ben More type, which dips below the 

 gneiss of Scounan. All the beds have a south-easterly inclination, 

 the gneiss at a higher angle. The grit rests upon the quartzite, 

 which abuts against the fault. 



This section throws light upon those just described. We here 

 see, as it were, the anatomy of the overthrow. The quartzite is 

 thrown down against the gneiss in nearly horizontal beds : and the 



* " Sgonnan Mor " on the Ordnance Map. Throughout this paper I have as 

 far as possible used the naming of the Duke of Sutherland's Map, as more 

 nearly representing the pronunciation. 



t It will be seen from his note that Prof. Bonney, without any knowledge of 

 my views on this point, infers that the grit " appears to have been greatly com- 

 pressed, as if nipped in a fault." 



