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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



[Feb. 6, 



along the higher part of the valley of Loch Maree. It is difficult to 

 give this rock any one specific name ; for, like that in Sutherland, 

 which we formerly described*, it varies greatly in mineral composi- 

 tion, even within a few yards. Near the limestone it is a serpentine ; 

 the green mineral then thins away, and quartz and felspar take its 

 place, while to these is occasionally added hornblende. The propor- 

 tions of the ingredients also vary to a large extent. 



This rock, by whatever name we designate it, occupies a large 

 part of Glen Cruehalie. Sometimes it lies only along the bottom of 

 the glen ; then it rises high on the one side, and soon ascends among 

 the slopes on the other. In some places it occupies indifferently the 

 place of the limestone, in other parts that of the quartz-rock or the 

 upper flaggy series, or it invades the three zones at once. But, though 

 it forms an important feature in the geology of the district, and oc- 

 cupies a considerable area, it does not interfere with the ascending 

 order, which is here, as everywhere to the north, quartz-rock, lime- 

 stone, and upper flaggy or schistose beds. 



The latter series of strata can be examined with advantage up the 

 ravine, along which the road winds from Kinloch Ewe to Auchena- 

 sheen. It consists of quartzose and micaceous flagstones and schists, 

 the south-easterly dip of which is well seen along the higher slopes 

 of the glen, the angle -varying from 25° to 50° These rocks clearly 

 overlie the limestone, and are as dissimilar lithologically to the Lau- 

 rentian gneiss (with which Professor Nicol would identify them) as 

 two groups of strata can well be. 



Loch Maree to Loch Torridon. — Few mountains in Scotland present 

 a more striking aspect than those which close in around the head of 

 Loch Maree, and stretch westwards to the Atlantic. Giant, sombre- 

 hued masses of Cambrian sandstone, in nearly horizontal beds, rise, 

 band over band, to a height of fully 3000 feet. Their summits are 

 not unfrequently capped with white quartz-rock ; and under certain 

 phases of the sky, when a gleam of sunshine falls on these hill-tops, 

 they seem in the distance as if tipped with snow. The illusion is 

 sometimes heightened by the faults, which let down the quartz-rock 

 in wedges among the dark-hued Cambrian beds ; for then the white 

 crags, descending some corry with a long stream of grey rubbish 

 below them, look like a stunted glacier, or an incipient avalanche. 



The general aspect of these hills is shown in the preceding dia- 

 grammatic section from the sea at Loch Torridon, across Loch Maree, 

 to Loch-na-Fad (fig. 9). The same geological characters mark the 

 high ranges from Leagach and Ben Eay to the Dingwall road at 

 Craig Inn. Some of the features of this tract it is necessary to 

 advert to more in detail. The rocks are faulted in a very extra- 

 ordinary manner; and these dislocations have been supposed to lend 

 some countenance to the hypothesis that the upper gneissose series, 

 which rests on the limestone, is the Laurentian gneiss, brought up 

 from the bowels of the earth by a convulsion of unknown magnitude. 

 It would indeed be strange if, in a country so metamorphosed and 

 mineralized, presenting so many crumphngs and contortions of the 

 * Quart. Journ. Geol. Soc. vol. xvi. p. 238. 



