340 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 21, 



Along the watershed to the N.W. of Coul-loch-beg the granite and 

 gneiss are again exhibited ; and at Maill Kean Loch Strathie and at 

 Craggen-dhu-na-riavaig the granite and gneiss are also apparent, 

 though the former is not so predominant as towards the S.E., but very 

 well- developed masses of gneiss occur with S.E. inclinations. Gneissic 

 rocks are also seen about Loch Peovaig, a small lake which forms the 

 source of the Rivagill Burn, which flows into the River Naver. Along 

 this stream-course, granite becomes rare, and the gneiss assumes a 

 flaggy aspect, is much flatter in its inclination than the gneiss on the 

 high ground to the S.E., and usually dips S.E. at about 20°. The 

 gneiss, as seen in the Eivagill, so far as lithology is concerned, pos- 

 sesses all the features which mark the upper or flaggy gneiss over- 

 lying the quartz-rocks and limestones of West Sutherland. 



The rocks on the east side of Strath Naver consist of gneiss, for 

 the most part of a flaggy nature, having the same S.E. dips which 

 obtain so abundantly in the country lying south-eastwards of this 

 Strath. At Betty Hill this group is alluded to by Sir Roderick 

 Murchison as being perpendicular, and pierced by granite ; and of 

 the rocks which occur between the Waver and Melvich, and from 

 thence eastwards to the borders of Caithness, Sir Roderick remarks 

 that they "must be classed with the newer gneissose flagstones, 

 though they are penetrated at such numerous intervals by bosses of 

 granite, that it would require much time and good detailed maps to 

 ensure their correct delineation" *. 



With reference to the coast section between the Kaver and the 

 Old Red Sandstones of the western margin of Caithness, although 

 the gneiss is often perpendicular, it still abundantly exhibits S.E. 

 dips. Gneiss having this inclination is well seen at Earr Bay, and 

 also at Swordly Bay. At these localities it is accompanied by 

 granite, and these rocks continue to Armadale, where the granite 

 becomes more abundant ; and between Strathie and Armadale the 

 latter seems to occupy almost exclusively the whole country, the 

 contour of which is comparatively flat and moory, features which 

 usually mark the occurrence of granite in East Sutherland. East- 

 ward from Strathie the Old Red Sandstone area alluded to by Sir 

 Roderick Murchison is seenf. Beyond this, at Sandside, bosses of 

 granite with crystalhne gneiss occupy the face of the country to 

 Reay, where the Caithness Old Red series commences. 



The section of this coast, so far as the gneiss and granite are con- 

 cerned, is very like that which is seen in the traverse between Achin- 

 toul and Strath Naver : and in both these sections, where the former 

 is not vertical, it has S.E. dips. The coast-section only exhibits an 

 extension north-eastwards of the strike of the rocks seen in the 

 interior, and justifies the conclusion that, with the exception of a 



blance in contour to the two Ben Griams. In consequence of the swampy con- 

 dition of this district I was unable to reach Ben Vaddu from the north ; but, 

 judging from its form, I am induced to look upon it as similar in composition 

 to the Ben G-riams, and consequently consider it as made up of Old Eed Con- 

 glomerate. 



* Quart. Journ. Geol. Soc, vol. xt. p. 237. t Op. cit., p. 403. 



