46 Scientific Proceedings, Royal Dublin Society. 



Plate X. Fig. 6. Is a section, drawn to scale, of tte deep 

 gorge or caiion of Braemore, at the head of Loch 

 Broom. The nature of this remarkable river-channel 

 has already been sufficiently described. 



Plate X. Fig. 7. The section at the Bridge of Atilt Corry, 

 near Ullapool, in which the following beds in des- 

 cending order are seen — all of the Lower Silurian 

 series : — 



S. 5. — Hard, massive, reddish pebbly grit at the 

 base of the upper qu.artzite — 6 feet thick. 



S. 5'. — Whitish quartzite in regular beds — 4 feet 

 thick. 



S. 4. — Thin band of shale and flags. 



S. 3. — Limestone in several beds with bands of 

 shale — 6 to 10 feet. 



S. 2. — Grayish sandy shale with fucoid markings. 



S. 1. — Upper beds of lower quartzite. 



General dip, E.S.E. at 5 to 6 degrees. 



Plate XL 



Plate XI, Fig. 8. Section taken across Ben Stack and Ben Arkle, 

 The former 2,364 feet, the latter 2,576 feet ia eleva- 

 tion; direction about W. to E. 

 Ben Stack, as already stated, is formed of dark horn- 

 blendic schists, &c., of Laurentian age (L), penetrated 

 by granite or pegmatite veins. The Cambrian sand- 

 stone being here absent, the Laurentian beds are 

 immediately overlaid by the lower quartzite (s. 1) of 

 the Lower Silurian series, forming the escarpment of 

 Ben Arkle ; this is followed by ferruginous sandy 

 shales, with fucoids (s. 2), then by the Assynt lime- 

 stone (s. 3), the glossy slates and flagstones (s. 4), 

 the upper quartzite (s. 5)yand finally by the micaceous 

 schists of the interior (s. 6), at the margin of which 

 the section ends. 



Plate XL Fig. 9. Section drawn across Quenaig, 2,240 feet, and 

 Ben More in Assynt, 3,281 feet, and passing a short 

 distance to the north of Inchnadamfi'. This shows 

 the basement hornblendic schists of Laurentian age 

 ( Ij), overlaid by Cambrian sandstone and conglomerate 

 (C), the beds of which are truncated along the eastern 

 side of Quenaig by the lower qiiartzite of the Lower 

 Silurian series. The succeeding beds are lettered 

 and numbered as in the preceding section. 



