376 C. CALLAWAY ON THE NEWEB GNEISSIC 



from the Torridon to the Dolomite. A similar discordance is seen 

 in Assynt. In Scounan and Ben More it lies upon Ben More Grit 

 (Torridon), npon the Quartzite in Ben Uarran and on Camaloch, and 

 upon the Salterella-quaxtzite on the south side of Loch Glen Coul. 

 At the head of Loch Glen Coul it rests indiscriminately on quartzite, 

 brown flags, and dolomite. 



Besides this, there is a frequent want of concordance in the 

 strike of the " Logan " and of the rock under it. Thus, on Loch 

 Glen Coul the normal direction of the Assynt series is to N.N.E., 

 while the strike of the gneiss which lies over it in the steep cliffs 

 is almost invariably to some point between W. and N.W. At the 

 actual contact there is sometimes conformity of dip, due, as I 

 believe, to the enormous pressure to which the rocks were subjected 

 during the overthrow ; but these coincidences are merely local. 



On Loch Glen Dhu, further north, the gneiss strikes E. and W„, 

 the Assynt rocks maintaining their N.N.E. direction. 



2. The " Logan Rock " not conformable to the rocks above it. — 

 It is impossible for two groups to exhibit a more marked uncon- 

 formity than exists between the " Logan " and the " Upper " 

 Quartzite of Ben More (fig. 6, p. 383). The gneiss is magnificently 

 exposed in the precipices which encircle the wild tarn of Dhuloch 

 More. The strike is usually to the N.N.E., in massive, almost 

 vertical, sometimes intensely contorted beds. The overlying grit 

 and quartzite are either horizontal or dip in an easterly direction 

 at a low angle. In the section on the south side of Coniveall, 

 already described in part (p. 372), the conglomerate and grit are 

 horizontal, and the gneiss is almost vertical. 



Ben Uarran is capped by nearly horizontal quartzite, while the 

 gneiss which appears at the west end has a high dip to E.N.E. 



The discordance is also seen at the north end of the summit of 

 Glasven, above Corry Dearg. The " Logan Eock " is sharply bent 

 into a syncline, into which the quartzite has sunk ; and, apparently 

 by a continuation of the lateral pressure, the quartzite is squeezed 

 into two or three overthrown folds combined with reversed faults. 

 These contorted beds are seen as in a vast diagram in the cliff 

 facing to the north, overhanging the loch. On the plateau above, the 

 continuation of these beds lies almost horizontally upon the high- 

 dipping gneiss. 



Similar facts are seen in Glen Coul, where quartzite, with a 

 gentle easterlv dip, rests upon gneiss striking at high angles to 

 W.N.W. 



The " Logan Eock " being in the highest degree unconformable 

 to the rocks both above and below, it can no longer be regarded as 

 a member of a continuous series. If there is no dislocation, there 

 must be two enormous breaks. Assuming the " Lower " Quartzite 

 to be Ordovician, the " Logan " must be at least Devonian, and the 

 " Upper " Quartzite can hardly be Palaeozoic at all. 



These reasonings have proceeded upon the assumption that in the 

 " Logan Eock " foliation corresponds with stratification — a theory 

 which, so far as I know, has never been disputed in reference to the 



