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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



[Dec. 5, 



example of gneiss conformably overlying' the limestone and qnartzite. 

 It might be sufficient to state that the rock which he describes as 

 gneiss is the intrusive granulite-rock of the last section*; but, as 

 illustrating the structure of the country, some further details are 

 necessary. 



At Heilam Inn, on Loch Emboli (fig. 4), the limestone dipping 

 10°-20°, to S. or S.E., but in broken flexured beds, forms both the 

 peninsula and the hill on the mainland to about the line of the road. 

 The next ridge consists of the quartzite, clipping on the west side at 

 65°, to W. 10° K., and on the east of the ridge 44°, to W. 5° S. 

 Crossing a small valley, the quartzite is again seen, dipping 83°, 

 W. 10° INT., and further on the fucoid-beds, dipping 64°, to S. 45° E. 

 The rocks are hidden for about 100 yards by grass and detritus ; 

 but at the foot of the cliff the same beds crop out, dipping in one 

 place at 20°, to E. 35° S., and in another at 6°, to S. 10° W. As 

 already stated, these beds are covered, not by gneiss, as in Mr. 

 Cunningham's figure, but by the granulite or eruptive rock form- 

 ing the great mass of the hill. It has clearly broken through the 

 strata, resting in one place on the fucoid-beds, in another on the 

 quartzite, and further east, towards Loch Hope, is overlain by 

 quartzose beds dipping 25°, to E. 30° S. 



The relations of the rocks in this section are quite clear and con- 

 sistent. No overlying gneiss is seen in it, and the mica-slate 

 is separated from the quartzite by the whole igneous mass of Ben 

 Arnaboll. The quartzite is, however, thrown east as far as Loch 

 Hope ; and the junction is then formed partly by the lake, partly by 

 the River Hope to its mouth. In the hills north-east of Hope 

 Ferry there is another outburst of igneous rock, here felspar- 

 porphyry ; and at Whiten Head it again appears in great force 

 in the line of junction, intruding partly on the quartzite, but 

 chiefly on the old slates to the east. In this trackless region the 

 sections are best seen in sailing along the coast ; but one single 

 fac t is decisive of the true relation of the mica-slate and quartzite 

 scries. North of Loch Hope Ferry the fucoid-beds and limestone 

 entirely disappear, and only the lower part of the series, or the 

 quartzite, comes in contact with the eastern gneiss or mica-slate. 

 This is the necessary resrdt of the beds along the line of fault 

 having been more exposed to denudation in the north, during the 

 gradual elevation of the land, from the wide and stormy northern 

 ocean, but is quite inexplicable on the hypothesis of conformable 

 upward succession. It has indeed been asserted that this is not 

 the quartzite below the limestone, but another quartzite above it. 

 That this is not the case is, however, proved by the quartzite near 



* See Cunningham, Geog. of Sutherland, p. 99, and plate 8. fig. 2. Though 

 a very acute observer and well acquainted ■with rocks, Mr. Cunningham has 

 in tliis and some other instances been misled by the strong Wernerian views on 

 the origin of certain rocks which he entertained. In consequence of this bias he 

 entirely mistook the nature of these igneous rocks, which were altogether over- 

 looked until I drew attention to them in the summer of 18.39. This is also true 

 of the similar rock on Loch More. Compare IS T ote, p. 94. 



