14 Mr. Macgillivray on the Granite of 



General Observations.— -These groups, separated from each other 

 by lower mountains and hills, send off long irregular ridges to- 

 wards the valley of the Dee, on the sides of which mica slate pass- 

 ing into quartz rock is principally seen. The relation of the gra- 

 nite to this rock I reserve for another occasion. 



The mountains of this district are very remarkable for their ex- 

 treme sterility, and the desolate aspect which they present. The 

 summits are rounded, sometimes nearly flat, to a great extent, and 

 entirely covered by disintegrating blocks and stone, together with 

 grit and sand, excepting in a few places where the singular protu* 

 berances mentioned above present themselves. Most of them ex- 

 hibit perpendicular precipices near the summit, which generally 

 assume the semicircular form, constituting the hollows named 

 corries, and having a lake at their base. The rock near the sur^ 

 face, wherever it is exposed, has split into tabular masses, gene- 

 rally pretty regular, and exhibiting the appearance of strata, in- 

 tersected by rectangular fissures. The true nature of these tables, 

 however, is readily understood on examining the precipices, where 

 they are best seen, and where, notwithstanding, the perpendicular 

 fissures more resemble the seams of strata. There is no tendency 

 in any part that I have seen to the concentric or globular arrange- 

 ment, nor do the masses in decomposing or disintegrating ever pre* 

 sent that appearance. 



In many cases, the granite, in decomposing, assumes a whitish 

 colour, but in general more or less of the red tint of the felspar is 

 preserved. In fact this tint, together with the long stripes of d©-- 

 bris along the torrents, has given their name to the Braeriach 

 mountains, brae signifying an upper district, and riach striped 

 with red. 



- Excepting along the slopes at the base of the precipices, it is 

 difficult to determine whether the blocks and stones which cover 

 these mountains are partially disintegrated and decomposed frag- 

 ments of the constituent masses, or of diluvial or other origin. 

 They are generally flattened or tabular, lie in all directions, and 

 at present have in very few places any decided appearance of be* 

 ing fragments broken and decomposed ifi situ. In other places, 

 where the rock appears at the surface, the disintegrated portions 

 lie in regular stratiform platep^ with little or no covering of debris^, 

 so that, upon the whole, it is not unreasonable to infer that the 

 greater part of the fragments has been produced by some cause dif- 

 ferent from ordinary disintegration effected by the weather in a 

 quiescent state of the earth's surface. A native of the district, on 

 being questioned by me as to what he conceived to be the origin of 

 this debris, said, " I dinna ken, but it has maybe lain there sin 

 Noah's flood." He thought it had no connection with the regular 

 mass of the mountain. 



; On the summits there are extensive tracts of grit and sand, 

 among which hardly any fragments occur, excepting occasionally 



