168 MR J. HORNE AND MR J. J. H. TEALL ON BOROLANITE. 



Ledbeg they have been so denuded as to present a prominent escarpment skirting the 

 road leading to Inchnadamff. But this conspicuous crag is by no means the western 

 limit of the mass. 



Ascending the Ledbeg River from the point where it joins the Ledmore River, 

 | of a mile east of Cama Loch, the coarse granitic rock is exposed at various points 

 in the stream section. About 70 yards to the south of Ledbeg Cottage the marble is 

 visible, and further up the stream, at the ford leading to the cottage, the basal bands of 

 the Durness limestone are met with in a highly altered form. A few yards to the west 

 of the river, and immediately to the north of the cottage, one of the bands of serpulite 

 limestone at the base of the Grudaidh group is clearly recognisable, though considerably 

 metamorphosed. Returning to the river, and following the section to a point about 200 

 yards above the footbridge, there are several excellent exposures of the granitic rock 

 penetrating the marble on both banks of the stream. Indeed the site of the old quarry 

 where the marble was formerly wrought is close by this locality, being situated a few yards 

 to the east of the river and near the road to Inchnadamff. The evidence that the marble 

 is merely an altered portion of the Durness limestone is still further strengthened by the 

 occurrence of recognisable bands of the basal limestone in an altered form, in a tributary 

 of the Ledbeg River, about 500 yards to the north of Ledbeg Cottage. Our colleague, 

 Mr Peach, who mapped this portion of the Ledbeg River, has traced the marble at 

 intervals from Ledbeg westwards to a point high up on the slope of Cnoc-an-Leathaid- 

 Beg, where it is associated with the pink granitic rock. At the latter locality the 

 marble and the intrusive granitoid rock are alike buried underneath the basal quartzites 

 and the " Pipe-Rock," resting unconformably on a slice of Lewisian gneiss. These 

 materials form an outlier separated by denudation from the displaced masses lying 

 above the Ben More thrust-plane. 



On the south side of the Ledbeg River, due south of the shepherd's house at Loyne, there 

 is another small outlier of shattered basal quartzite, separated by a powerful thrust-plane 

 from the underlying materials. Measuring about 700 yards in length and about 400 

 yards in breadth, these displaced quartzites rest partly on thrust " Fucoid Beds," 

 serpulite grit and basal limestone, and partly on the marble. Along the eastern limit of 

 this outlier a line of swallow holes can be traced, and the marble is visible in a 

 conspicuous grassy patch of ground adjoining the basal quartzites about 500 yards to the 

 south of the river. Crossing the flat peat-covered ground to the south of this exposure, 

 the marble is again seen in a small rocky knoll within 50 yards of the boundary line of 

 the granitic mass of Cnoc-na-Sr6ine. From the latter point the boundary line of the 

 igneous rocks sweeps eastwards along the southern slope of the valley to the base of 

 Ruighe Cnoc, where there is a fine escarpment of the pink granitic rock. For most 

 of this distance the junction of the intrusive mass with the thrust Cambrian strata is 

 buried under peat and drift. 



But on the north side of the valley, about 150 yards to the north-east of the Loyne 

 shepherd's house, there is a detached mass of the pink orthoclase rock of Cnoc-na-Sr5ine in 



