K0CKS OP THE NOKTHEKN HIGHLANDS. 407 



fault, which here runs along the cliff. I could not at the distance 

 determine whether the gneiss was Hebridean or Caledonian, but 

 the colour was that of the latter. 



Ground between Druim-an-tenigh and Ben Arndboll. — Between the 

 inverted synclines on the western slopes of these parallel ridges the 

 rocks are very broken. North of the little loch in the intervening 

 valley, the Salterella-zone with overlying dolomite was repeated 

 more than once. The strike of these beds, when continued to the 

 north, diverged more and more from the strike of the Assynt rocks in 

 the escarpment ; and just above Loch Craggie a mass of Annelidian 

 Quartzite, with strike at right angles to the beds on each side, came 

 in. It really seemed as if this were a wedge thrust in from the north, 

 and that it had forced apart the faulted strips between which it had 

 been intruded. 



Yery striking evidence of lateral pressure is seen in this quartzite. 

 The worm-tubes, originally vertical, are all strongly bent towards 

 the west. The contortion is even more marked than in the tubes of 

 the quartzite at the Stack of Glen Coul. As this mass is out of 

 place, the side pressure must have been subsequent to the faulting. 

 In a small hill to the west the same phenomenon is repeated. The 

 next ridge to the west is composed of the Flags, which are bent in 

 different directions and terribly broken, fragments of quartzite 

 being also thrust in amongst them. This ground has been described 

 to supply corroborative evidence of lateral thrust and dislocation. 



D. Outliers of the Assynt Series on the Caledonian. 



Nicol, in his Camas- an-Duin section*, represents an outlying 

 fragment of quartzite on the top of his " intrusive granulite." As 

 the latter rock is certainly a gneiss ; the quartzite is to be regarded 

 as a true outlier. I have detected two other outlying patches on 

 the plateau between the Arnaboll valley and the point where the 

 quartzite comes up to the Hope gneiss, so that they all rest upon 

 the Arnaboll group, which here forms lower ground than the Hope 

 rocks. One of these outliers (see fig. 8, p. 399) lies a little north of the 

 point where the Arnaboll gneiss ; disappears, and a second a short 

 distance on the strike to the north of the first. They are not far to 

 the east from the junction between quartzite and gneiss, the latter in 

 both cases clearly intervening between them and the chief mass to 

 the west. They are composed of the basement beds of the quartzite, 

 seamy and gritty. The dip is easterly at a low angle, the rock 

 being somewhat disturbed, as if exposed to subsequent compression. 



A third mass of quartzite forms a boss on the top of the southern 

 slope of the Arnaboll valley at its eastern end. The strata plunge 

 about at various angles in almost every direction. On the north side, 

 the lowest bed, the conglomerate, dips IS", at Arnaboll, gneiss also 

 dipping 1ST., the usual dip of the gneiss in this locality being S.S.E. 

 On the western face of the knoll the quartzite dips S.E., as if away 

 from a mass of gneiss which rises on the west. 



* Quart. Jouru. (Jeoi. Soc. I860, vol. xvi. p. 88. 



2g 'jl 



