TRANSACTIONS OF THE SECTIONS. 117 



Ben Macdhui (only rivalled in Britain by Ben Nevis) and the Cairngorm mountains 

 on the north of the Dee ; and on the south of that river, Loch-na-gar, Mount Keen, 

 Mount Battock, and other giants of the Southern Grampians. These, the principal 

 mountains, are usually round, massive, dome-like, with a deep corry on one side as 

 if formed by the falling in of one-third of the mountain, and thus bounded by lofty, 

 rudely prismatic precipices rising from a dark black tarn in the centre of the hollow. 

 In consequence of decomposition the granite mountains are usually covered with 

 huge feather-bed-like rocks piled up in cairns of rude masonry, and the shelter of the 

 red deer and ptarmigan. The rock in these mountains is rather fine-grained, 

 uniform in structure, and often reddish coloured. It contains cavities in which the 

 rock-crystal or Cairngorm stone, the topaz and the beryl are found. Bennachie, 

 one of the outposts of these mountains on the north-east, though not high and easily 

 accessible, is very interesting. It looks out on the south-west to the loftier ranges 

 of the Grampians, with patches of snow even at the end of summer : and on the north- 

 east over the plains of Buchan — low, undulating, and treeless, but rapidly changing 

 under the industry of the inhabitants from bleak moors to fertile corn-fields. 



A large portion of these north-eastern plains, too, consists of granite ; in them, 

 however, occupying the lowest, not the highest position, as in the mountains. This 

 fact shows that the granite is the basis on which the strata rest, and hence is ex- 

 posed where they have been cut away by denudation. A fine section of the granite 

 is seen in the sea-cliffs south from Peterhead, where it is intersected by long narrow 

 gullies and deep caves, in which the restless surge of the North Sea keeps up an 

 incessant tumult. Hence some of the more remarkable of these excavations have 

 got their name of the " Bullers of Buchan." 



The rock in this region is red or grey, according to the colour of the felspar. It 

 often contains hornblende, or is a syenite, as in the tract to the north of Huntly, 

 and in other places again becomes almost a fine-grained greenstone or diorite. This 

 diversity of mineral character proves that the granite is not all of one period of 

 formation. The veins of granite in the granite itself show this even more clearly. 

 These are beautifully seen in Rubislaw quarry, close to the town, where there is one 

 very remarkable vein of coarse granite composed of very large twin crystals of ortho- 

 clase-felspar, and mica in a basis of quartz along with long broken prisms of schorl, 

 Davidsonite or impure beryl, and garnets. The quartz in this vein is also remark- 

 able for numerous cavities enclosing fluids. 



Of the stratified rocks, the first, gneiss, covers a wide extent in Aberdeenshire, and 

 generally in close proximity to or resting on the granite. It is thus seen in the 

 valley of the Dee above Braemar, reposing on the granite in thin even beds at a low 

 angle, and apparently undisturbed by the inferior igneous rock. In many parts of 

 the low country the same relation occurs, the gneiss often forming the hills, the 

 granite the intervening valleys. But in other cases, as in the hills north of Ballater, 

 the two formations are seen side by side. The gneiss in many localities is full of 

 granite veins ; but whether these belong to the great mass of granite or are of a 

 different age, is not easily determined ; and the question seems never to have been 

 fully or fairly worked out. Such veins are well seen on the coast to the south of 

 this city, especially near Girdleness and the Cove, and also in many parts of the 

 mountain chain on the south side of the Dee. Veins of felspar-porphyry, and of 

 trap, are known in the gneiss on the same coast and in many other localities. 



The gneiss is usually the common variety of quartz, felspar, and mica. But 

 varieties with hornblende passing into hornblende-slate are also common. The latter 

 are well seen in the hills along Glen Muic and up to the top of Morven. The beds 

 of gneiss are seldom flat or even, more often highly contorted. 



In the Braemar district the gneiss is covered by beds of limestone and quartzite — . 

 the latter perhaps only a variety of the gneiss. It often contains much magnetite, 

 apparently replacing the mica. Indeed iron, both as the oxides and the pyrites, is 

 very common in all these rocks ; strongly impregnating many of the springs, and 

 finding its way into the sands of the rivers and of the sea-shore. From the Cairngorm 

 mountains great ridges of quartzite run north into Banffshire and to the coast near 

 Cullen. In some places in this region it appears to lie below the mica-slate, but 

 their exact relation is obscure. In other parts of the low country, as in Mormond 

 Hill, the quartzite rests on the gneiss. 

 Mica-slate in Scotland is most common in the South-west Grampians ; but in this 



