Rev ieivs — Oeology of Central Ross-sh ire. 277 



The mean annual rainfall exceeds 60 inches, while at Loch Torridon 

 and Glen Carron, situated in narrow glens among lofty mountains, 

 the average fall is respectively 88'58 and 90-23 inches, and at the 

 latter station has reached as high as 109 inches for one year. 



This tract of country may be described as a more or less denuded 

 high mountain plateau, falling towards the north-east and reaching 

 its greatest elevation along a line drawn from Eeinn Eighe, in the 

 north-west corner of the map, to An Riabhachan and Sgurr na 

 Lapaich on the southern margin. The most obvious features in the 

 surface-relief are the three through- valleys which cross the region 

 in a nearly parallel E.N.E.-W.S.W. direction. 



Ten rivers and eight lakes (or lochs) bespeak the abundant rainfall 

 of the district, while Loch Torridon and Loch Carron, the heads of 

 fiords, are obviously tlie seaward extension of drowned valleys pre- 

 glacial in origin and formed when the land stood at a higher level 

 than at the present time. Subsequent glacial erosion produced 

 over-deepening of the valleyj? and excavated a succession of rock- 

 basins, now all beneath sea-level, in their floor, but they were in 

 all probability partly eroded below the present sea- level before the 

 glaciation of the country. After the disappearance of the ice from 

 the lower part of tlie valleys, moraines, fluvio-glacial gravels, raised 

 beaches, and river alluvia were left behind very generally, partially 

 filling up many of the lochs with moraine deposits. 



Turning to the solid geology depicted on the map, one is struck 

 by the great antiquity of the rock-groups which form the entire 

 area. Thus "The whole of the ground east of the lliver Carron and 

 of a line drawn from Achnashellach to Kinlochewe is occupied by 

 crystalline metamorphic rocks — the siliceous and perlitic schists of 

 tlie Moine Series — surrounding inliers of complex gneisses of Lewisiau 

 type. The latter are most widely developed in the eastern part of 

 the area, where the largest inlier is found in the basin of the Meig, 

 and forms a great part of the mountain Sgurr a' Gblas Leathaid. 

 Other smaller masses occur in Glen Orrin, in Glen Strath Farrar, 

 and round ihe head of Loch Monar. These inliers are all east of the 

 ' Moine thrust'. 



" Another large mass of Lewisian Gneiss enters the map on either 

 side of Locli Carron, and is continued as a narrow and interrupted 

 belt along the west side t>i Strath Carron, and northwards through 

 the Coulin Forest to within a short distance of Kinlochewe. This 

 western belt forms part of the thrust masses situated west of the 

 Moine thrust ; the portion south of Locli Carron lies to the east of 

 tliat line of movement. A portion of a small inlier of unmoved 

 Lewisian rocks appears on the western margin of the map 2+ miles 

 north of the head of Loch Torridon. 



"The remaining north-western portion of the sheet is occupied by 

 sedimentary rocks of Cambrian and Torridonian age, these two 

 formations alternating in parallel belts along lines of thrust or natural 

 outcrop; while, in the unmoved area, the Cambrian quartzites cap 

 the liighest peaks of Laitliach and Beinn Eighe" (p. 10). 



Sixty-four pages (chapters iii to viii) are occupied with a detailed 

 account of the Moine thrust and its effect upon the tectonics of the 



