372 C. CALLAWAY ON THE NEWER GNEISSIC 



fault. As rocks of the same zone occupy the ground on both sides, 

 there can be but little throw, even less than on Poulan-drein. In- 

 deed this fault can be little more than a crack caused by the syn- 

 cline being compressed to fracture. Higher up the quartzite is 

 underlain by rocks of the seamy type, with felspar bits and intru- 

 sions of felsite and diorite. Eeaching the summit of the western 

 spur (1800 feet) of the mountain, we find these beds squeezed up 

 against a mass of gneiss into several very closely appressed folds. 



Returning to Glenbain, we start, in the opposite direction, to the 

 south-west. The Dark Dolomite, dipping S.W., is followed by the 

 white Dolomite, which lies in a syncline, on the S.W. side of which 

 reappear in regular succession all the members of the Assynt series. 

 The outcrop of the higher subdivisions forms the precipice over- 

 hanging the high road between Stronchrubie and Inchnadamff, the 

 Quartzite and Torridon rising into the well-known mountain-masses 

 south of Loch Assynt. 



We have in this important section an indubitable syncline, the 

 northern side of which has been thrust laterally by the mass of 

 gneiss, so that the dip is higher, and the rock is sharply contorted. 

 The section is unbroken, except at the narrow interval, a few yards 

 wide, occupied by talus ; but the Annelidian Quartzite occurring on 

 both sides of it, there is no reasonable doubt of the completeness of 

 the series in both halves of the syncline. If this reading is correct, 

 we must admit that the " Lower " Quartzite of Canisp, after passing 

 under the basin of dolomite, is transformed into the " Upper " 

 Quartzite of Ben Uarran ! 



I may be permitted to revert to an argument adduced in a pre- 

 vious paper*, and which a more detailed study of the ground brought 

 home to me with irresistible force. What has happened to the 

 northern side of the Stronchrubie basin in its prolongation to the west ? 

 Near Glenbain the series is complete down to the Annelidian 

 Quartzite ; but west of Poulan-drein, a distance of from 500 to 600 

 yards, the whole has vanished. What has become of it, if it is not 

 faulted out ? And if it is faulted out, the argument for an " Upper " 

 Quartzite, so far as Murchison's celebrated Cnoc-an-drein section is 

 concerned, falls to the ground. 



Section in the Balloch under Coniveall (fig. 6, p. 383). 



This is the second locality where the Dolomite is alleged to pass 

 below an " Upper " Quartzite. I may freely admit that an observer 

 who had not studied the district in detail might naturally form 

 Murchison's opinion. On the west side of the pass we see clearly 

 exposed the typical series from the Quartzite, full of il worm-holes," 

 to the Dolomite, the whole dipping E.N.E. at 40°. At the south 

 end of the gap the Dolomite appears to dip below quartzite. 



That there is an unbroken succession here is refuted by the fol- 

 lowing considerations :— 



(1) The White Dolomite and the greater part of the Dark Dolo- 

 mite are absent, the thickness of dolomite being very slight. The 

 * Quart. Journ. Geol. Soc. 1881, vol. xxxvii. p. 243. 



