the Upper Districts of Aberdeenshire. 



17 



Loch Muic is about two miles long. Its waters are dark-coloured, 

 and it contains abundance of small trouts^ but no salmon, a fall of 

 the river preventing the latter from ascending. The rills which 

 enter this lake are all dark-coloured, owing to their being impreg- 

 nated with peat, which to a greater or less depth covers all the 

 lower parts of the Loch-na-gar group. This arises from the cir- 

 cumstance that the granite of that group is much less decomposed 

 than that of the mountains to the north of the Dee. This may- 

 seem strange to some, inasmuch as disintegration is generally sup- 

 posed favourable to vegetation. But let it be remembered that 

 the deepest accumulations of peat are generally upon rocks which 

 appear to have undergone no disintegration, as may be seen in the 

 Outer Hebrides, and especially in the islands of Uist and Lewis. 



Structure of Granite. — Geologists speak of the stratification 

 of granite, and I have anxiously looked for appearances of it 

 in the numerous precipices presented by the mountains. The 

 tendency to form pretty regular cracks or fissures, generally ap- 

 proaching the perpendicular, is decided, and in the faces of the pre- 

 cipices might easily be taken by a careless observer for the seams of 

 strata. But these fissures, although frequently parallel, are not 

 always continuous in the whole of the exposed surface, and often 

 terminate abruptly, while at other times they run obliquely to 

 the general direction. In short, they greatly resemble those of many 

 of the trap rocks, as of the Castle Rock of Edinburgh, but on a 

 larger scale. On the other hand, the tabular pieces into which the 

 rock resolves in becoming disintegrated, and of which the protube- 

 rances on the summits, and the upper parts of the precipices con- 

 sist, might still more decidedly lead to the supposition of their be- 

 ing strata. These tabular masses, however, are only seen on the 

 more exposed parts of the precipices, towards their summits, and 

 on the edges of the great fissures, and never appear in the lower 

 and more solid parts. 



VOL. III. 



