IN THE NORTH-WEST HIGHLANDS OF SCOTLAND. 401 



reaching a considerable elevation. In one case, a Pre-Cambrian 

 hill, about 700 feet higJi, projects through the lower, and is over- 

 lapped by the higher members of the Eed-Sandstone series on the 

 north-west slope of Quinaig. Similar evidence, though not so 

 remarkable, is obtained round the margin of the outlier at Stoer 

 north of Lochinver, on the shores of Cama Loch near Elphin, and to 

 the south of Loch Broom. 



2. Order of Succession in the Parph District, 



The general ascending order of succession in the Parph district 

 is as follows : — 



(4i. Fine-grained, friable, yellow and mottled sandstones and 

 I marls. 



m , 1 3. Alternations of coarse sandstones, grits, and beds of con- 



I glomerate, 



maximum _^ ^^ Conglomerate, containing well-rounded pebbles of slaggy 



maximum 

 thickness 

 1800 feet. 



diabase-porphyrite, quartzite, greywacke, hardened 

 shales, cherty limestone, jasper, &c, 

 1. Angular basal breccia, occurring at any horizon where the 

 \^ domes of gneiss project through the Cambrian deposits. 



Of the foregoing subdivisions, zone 2 presents features of special 

 interest, as the component pebbles have not been derived from the 

 underlying gneiss. They point to the existence of an older series of 

 sedimentary deposits and volcanic rocks, no trace of which has yet 

 been met with throughout the Archaean area*. 



3. Succession in Assynt. 



In Assynt the foregoing subdivisions cannot be traced, as the 

 vast thickness of strata mainly consists of coarse sandstones, grits, 

 and occasional bands of conglomerate corresponding with zone 3 of 

 the above section. Towards the base, however, the beds become 

 flaggy and fine-grained and contain several bands of purple and 

 greenish-grey shales and sandstones. In places there is an 

 important local development of conglomerate named " the Button 

 Stone," which seems to have filled hollows in the old land surface. 

 This horizon has been of great service in the identification of the 

 masses of Cambrian strata thrust forward by the Post-Lower- 

 Silurian displacements. 



At Stoer north of Lochinver there is a small patch of Cambrian 

 strata, covering about six square miles of ground, which possesses 

 special interest owing to the discovery of organic remains in grey, 

 green, and black mudstones and cornstones near the base of the 

 series. The fossils consist of calcareous rods, which have as yet 

 defied determination. The total thickness of the members of this 

 formation in Assynt varies from 3800 to 4000 feet. 



* The occurrence of rocks foreign to the North-west Highlands, in the Cam- 

 brian conglomerates of Koss-shire, has been chronicled by Dr. Hicks (Q. J. G. S. 

 vol. xxxiv. p. 813). 



2e2 



