124 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jail. 21, 



stone in several places round the mountain adds farther probability 

 to this view, although the exact nature of the connexion between the 

 quartz-rock and the limestone is not distinctly seen. Both Playfair 

 and MacCuUoch represent the stratification of the quartz-rock of 

 SchiehalHon as nearly vertical, and undoubtedly the principal divi- 

 sional planes are nearly perpendicular, with a direction of W. 10° N. ; 

 but there is another set of divisions nearly horizontal, which, though 

 less marked than the former, may represent the original stratification 

 of the sandstone*. Nothing can be more fallacious than the view, 

 suggested by the map, that the quartz-rock separates the gaeiss from 

 the mica-schist in this part of Scotland : the quartz-rock forms no 

 such continuous band as is represented, and the gradual passage from 

 gneiss into mica-schist may be seen in innumerable places. 



There are several other important tracts of quartz-rock which I 

 have not seen, and can only allude to slightly. 



In the south of Caithness, the range of the Scarabins, *' entirely 

 composed," according to Professor Sedgwick and Sir R. I. Murchison, 

 " of beautifully white compact quartz-rock," is encircled by old red 

 sandstonef. This, therefore, without belonging to the Gneiss, seems 

 to be of a formation anterior to the Old Red Sandstone. 



A large part of Banffshire is formed of quartz-rock, which is laid 

 down both on MacCulloch's map and on the more detailed map of 

 that county by Mr. Cunningham;^. The great mass of quartz-rock 

 on the coast near CuUen seems to belong to the Old Red Sandstone, 

 with which it is continuous ; but all the narrow strips of quartz-rock 

 which occur in the schistose district of the county appear, from Mr. 

 Cunningham's map and description, to be interlaced with the gneiss 

 and mica-schist, and to have the divisional planes conformable to the 

 foliation of those rocks : so that it must be presumed that they be- 

 long to the Gneiss. 



MacCulloch has described at some length the quartz-rocks of Jura 

 and Isla§ : it would seem that there are in those islands quartz- 

 rocks belonging to both the classes which I have been endeavouring 

 to establish. The conglomerates with pebbles and fragments of 

 quartz and jasper in Jura ||, and the conglomerates of Isla^ are clearly 

 sedimentary formations, with which the limestones of Isla are asso- 

 ciated : on the other hand, the direction and dip assigned to the di- 

 visions of the great formations of quartz-rock through both islands 

 agree sufficiently with that of the foliation of the gneiss and schists 

 on the neighbouring land to make it probable that a large proportion 

 of the quartz-rock is connected with that class of rocks. 



It may be of some importance to point out to the agriculturists 

 that the principal deposits of limestone throughout the Highlands lie 



* Playfair says of these, " the rock is much cut by fissures transverse to its 

 stratification." When I visited Schiehallion in 1849, being prepossessed with the 

 notion that the rock was vertical, I omitted to note the dip of the transverse di- 

 visions, of which I have a distinct recollection. 



t Trans. Geol. Soc. 2nd series, vol. iii. p. 128. 



J Journal of the Highland Society, No. 57, for June 1842. 



§ Western Isles, vol. ii. pp. 208, 239. 



II Log. cit. p. 210. ^ Loc. cit. p. 250. 



