IN THE NORTH-WEST HIGHLANDS OF SCOTLAND. 439 



the deposition of the Old Red Sandstone. Between Ben Loyal 

 and the Kyle of Tongue various outliers of this formation, de- 

 scribed by the present Director-General of the Geological Survey, 

 rest on a highly eroded platform of the crystalline schists. The 

 deposits are also met with in the islands at the mouth of the Kyle. 

 One of these outliers, at Cnoc Craggy (1043 feet), about a mile and 

 a quarter to the north of the northern margin of the Ben-Loyal 

 syenite, was grouped by Professor Nicol with the Torridon sand- 

 stones, and was believed by him to be overlain by quartzite*. The 

 platform on which it rests is about 800 feet high. Upwards of 40 

 per cent, of the pebbles in the conglomerate are composed of the 

 syenite of Ben Loyal. It follows, therefore, that the latter intru- 

 sive sheet was stripped of the overlying schists, thus proving enor- 

 mous denudation before the deposition of the Old Bed Sandstone. 



Some of these outliers, on the east side of the Kyle of Tongue, 

 rest on the Moine flagstones produced by the Post-Lower-Silurian 

 movements, and they contain numerous fragments of these schists. 

 Hence it is obvious that the changes must have been completed 

 before the time of the Lower Old Red Sandstone. 



Purther evidence that the outliers really belong to the Old Red 

 Sandstone is furnished by their numerous pebbles derived from the 

 Cambrian and Silurian formations. Amongst these, we noted Cam- 

 brian sandstones, false-bedded quartzite, " pipe-rock," Serpulite-grit, 

 and limestone belonging to several groups of the Durness limestone, 

 some of the blocks containing Mui^chisonia. From the inclination 

 of the layers in the conglomerate it is evident that the pebbles 

 were borne by currents from the W.N.W. 



The detailed examination of the north-west of Sutherland has 

 furnished important evidence regarding the glaciation of the region, 

 showing, for example, that during the greatest extension of the ice 

 the centre of .dispersion did not coincide with the existing range of 

 high ground. It has also thrown light on the excavation of the 

 present valley-system, on the relation of disruption-lines and the 

 trend of basic dykes to surface-features, and, finally, on the formation 

 of lofty mountains by denudation. But the description of these and 

 other phenomena is reserved for the detailed official memoirs of the 

 Geological Survey. 



Discussion. 



The President observed that the communication just made to 

 the Society was remarkable, not only for its importance, but for the 

 mass of details it contained ; it was, in fact, four or five papers rolled 

 into one. 



Professor Lapwoeth commented on the wonderfully descriptive 

 character of the paper. The general conclusions arrived at were very 

 similar to those he had himself indicated. There was this difference 

 that when he brought forward his views such notions were novelties 

 and were consequently regarded with suspicion. But so much has 

 the question been ventilated within the last four years that he pre- 



* Quart. Journ. Geol. Soc. vol. xvii. p. 92. 



