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PROCEEDINGS OP THE GEOLOGICAL SOCIETY. 



[Feb. 6, 



flowing down a deep, precipitous gorge, enters the head of Loch 

 Maree. Where the stream quits Loch-na-Fad, the Cambrian sand- 

 stone sets in, extending up the loch and down the river, and rising 

 up into the great mountain-masses already referred to. The descent 

 of the ravine of the Hassac, by a tortuous and usually imperceptible 

 track, brings before the geologist a noble natural section. On the 

 south, or left side, the Cambrian strata rise for some way up the 

 cliff, capped by the white and grey beds of quartz-rock. On the 

 other side the latter strata are absent, and the Cambrians form the 

 craggy scarps of the ravine, till they are succeeded further down by 

 the subjacent Laurentian gneiss. 



Loch Maree. — Loch Maree, one of the wildest of Scottish lakes, 

 presents a series of sections of singular clearness. With Kinloch 

 Ewe as his head-quarters, the geologist has a wide sweep of in- 

 teresting ground around him ; and we know of no locality where he 

 may better acquaint himself with the order of superposition of the 

 ancient crystalline rocks of the Highlands, or with the dislocations 

 and metamorphism which they have undergone (fig. 8). 



The occurrence of the Laurentian gneiss on the banks of this lake 

 has been already described in this memoir, as well as the superjacent 

 Cambrian sandstones, and the inferiority of these to the white quartz- 

 rock. From the mouth of the Hassac river, up the valley, to the 

 opening of Glen Cruchalie, the quartz-rock forms the north-eastern 

 side of the valley ; . for the Cambrian strata rapidly dip below the 

 surface. A felspathic rock, however, occupies the lower part of the 

 cliff, and even rises to a considerable height above the valley. The 

 same, or a similar mass, occupies, as we shall immediately see, a 

 large part of Glen Cruchalie. 



The quartz-rock dips in a south-easterly direction, at various 

 angles, up to 35° or 40°. It is worthy of remark, that it extends 

 further south-cast on the northern side of Loch Maree than on the 

 southern. On the former it continues to the line of Glen Cruchalie, 

 where it is overlain by the limestone ; on the latter it ends at or 

 near the Inn of Kinloch Ewe, where, in the bed of the stream, are 

 flaggy gneissose beds, indicating the upper series. The strata on 

 the one side of the valley, if prolonged across, would abut against 

 the edges of a different set of strata. Either, therefore, there must 

 be a very sharp and sudden change in the strike of the rocks between 

 Glen Cruchalie and Kinloch Ewe, or a fault must traverse the valley 

 along the line of Loch Maree. The latter explanation is probably 

 the true one. This fault, however, it is needless to remark, does 

 not in the least degree obscure the order of succession. 



The upper beds of the quartz-rock are well exposed in Glen 

 Cruchalie. They dip south-easterly, at 35°, and show large surfaces 

 covered with annelide-burrows. They are immediately succeeded by 

 beds of bluish-grey and red mottled limestone, with shaly bands, 

 having the same general inclination. 



In Glen Cruchalie the most marked rock is one similar to that 

 which was described as overlying the limestone at Loch-na-Fad, 

 and underlying the quartz-rock at the mouth of the Hassac and 



