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character and loose gray blocks on one part, and the grassy or 

 heath-covered slopes, with dark terraced ledges, on the other ; and 

 the geologist is therefore prepared to find a junction somewhere here 

 in such a natural section as the river affords. It occurs about 

 two or three dozen yards below the point where the Rosa burn 

 receives from the west side its only tributary the Garbh-Alt 

 or Kough burn, which drains the whole eastern side of the Ben- 

 G-hnuis range, and comes down into the glen, bounding headlong 

 across the huge granite sheets in a series of striking falls. The 

 junction has not been so well shown these few years (1855-58) 

 as it was formerly, in consequence of the accumulation of loose masses 

 of granite ; still it is sufficiently well seen to make the place interest- 

 ing and instructive in a high degree, and some future floods in the 

 river may again open it better up. The slate is greatly altered for a 

 considerable distance down the stream, and pervaded by small veins 

 and strings of quartz, and granite in which quartz predominates. 

 The colour of the slate is changed, having more of blue than is usual 

 to it ; the structure is altered also, the laminae are contorted and 

 present thin bands of different colours, chiefly blue and gray ; 

 the latter being purely siliceous, that is, flinty slate or quartzite with- 

 out the colouring matter, iron or manganese, which exists in the 

 former. The slate on this side of the mountains is generally a dark- 

 coloured coarse siliceous rock, showing shining crystalline flakes in 

 fresh fractures; in some places assuming that arenaceous semi-con- 

 glomerate structure which used to be designated as greywacke. Both 

 structures are obliterated on approaching the granite ; the colour is 

 bluish, or blue and gray in alternate bands, the structure is extremely 

 fine-grained, and the hardness and toughness are both excessive. 

 These changes, the contortion of the laminae, or the total disappear- 

 ance of all stratification, coupled with other modifications not seen 

 here, but to be again noticed, clearly indicate that the schist to a 

 considerable distance from the granite was subjected to intense heat, 

 and remained in such a state of at least semi-fusion as to permit, 

 under the action of chemical forces, a new arrangement of parts, and 

 the permeation and interlacing of veins from the molten rock below. 

 The granite veins are less numerous, smaller, and of varieties differ- 

 ing from the ordinary type of this rock more than is usual in most 

 other junctions with the slate ; such might perhaps be seen in the 

 interval of several yards here obscured before the granite itself is 

 reached. The great extent of the altered slate seems to indicate 

 that the strata near the junction are of inconsiderable thickness, and 

 that the granite exists beneath at a small depth, as shown in the 



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