1856.] NICOL — aUARTZITES, ETC. OF N.W. SCOTLAND. 



17 



The following Table exhibits a comparative view of the composition 

 of the allied mineral substances alluded to above : — 



AUophane 





Silica. 



Alumina. 



Water, 







Beauvais 



Charlton 



Ezquerra 



Scarborough .. 

 Fins 



21-90 



18-89 



15- 



10-50 



41-65 



41-78 



44-94 



29-20 1 44-20 Clay 4-7 Berthier. 



Q'l.ciO dO'T^ n^-u ^: _ a. to t\:-\. 



KoUyrite 

 Scarbroite 

 Pholerite .. 



44-5 i 40-5 



V^tUU. iiUiC t oo 



Berthier. 



Vernon. 



Guillemin. 



42-50 ; 46-75 

 43-35 15- 



Ox. iron -25 



5 



36-99 

 39-06 



14-26 

 1600 



Peroxide of iron 

 4-51, magnesia 

 •16, lime -48 



Halloysite 



Anglar 



► Dick. 

 Berthier. 



3. On the Red Sandstone and Conglomerate, and the Super- 

 posed Quartz-rocks, Limestones, and Gneiss of the North- 

 west Coast of Scotland. By James Nicol, F.R.S.E., F.G.S., 



Professor of Natural History, jMarischal College and University, 

 Aberdeen. 



Contents. 



Introduction. 



Sections in the Northern part of the District. 



Loch Broom (north side). 

 ,, „ (south side). 



Loch Assynt. 



Kyle of Durness and Loch Eriboll. 

 Sections in the Southern part of the District. 



Gairloch and Loch Maree. 



Loch Keeshorn. 



Southern part of Skye. 

 Order of the succession of the rocks. 

 Organic remains and markings. 

 Distinctive physical characters of the rocks. 

 Probable age of the rocks. 

 Conclusion : Geological history of the north-western district of Scotland. 



Introduction. — The Red Sandstone and Quartzite rocks on the 

 north-west coasts of Sutherland and Ross possess many features of 

 interest, which have long attracted the attention of geologists. The 

 mountains, rising abruptly from the great table-land of lower hills in 

 smooth rounded cones, spiry peaks, or long serrated ridges, their 

 hoary summits shining in the sun like new-fallen snow, and sending 

 down streams of rugged fragments to the deep sea-lochs that, running 

 far up into the interior, wash their bases, present scenes of wild and 

 varied grandeur unknown in other parts of the island. Nor does a 

 closer examination lessen the wonder with which we regard these 

 mountains. They are then found to consist, not of granite or igne- 

 ous rocks, nor of the older so-called primary strata, crushed up and 

 broken by some great convulsion, as their singular outlines might 

 have led us to expect, but of stratified rocks of no great hardness, lying 



VOL. XIII. PART I. C 



