382 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 1, 



Overlying Micaceous Flagstones and Younger Gfneiss. — ^In the masses 

 which overlie the quartz-rocks and limestone, we no longer find the 

 same uniformity of lithological composition as in the lower strata. 

 In the earKer deposit, mica is absent ; but in the higher masses, that 

 mineral begins to prevail. Here and there, as we leave Assynt and 

 Durness, and proceed to the E.S.E., it occurs in otherwise pure 

 light-grey and whitish quartz-rock, and at others in dark-grey mica- 

 ceous schists. Independently of dislocations and partial axes of eleva- 

 tion (one of which has been described as seen between Durin and 

 Rispond, whilst another is met with at the south-eastern end of Loch 

 Eribol, where granite protrudes), the micaceous part of the quartz- 

 ose series is observed to be superposed, as a whole, to the group in 

 which the limestones and their fossils occur. Erom Loch Eribol 

 the strata have a persistent dip to the east by south. (See Sec- 

 tion, fig. 8.) 



From the western coast-cliffs of Cape "Wrath to the bay called the 

 Kyles of Tongue, there can, indeed, be no sort of doubt that the 

 whole series of quartzose and calcareous rocks which overlie the 

 older gneiss and the Cambrian conglomerates, are, in their turn, 

 covered by the younger micaceous flagstones of Inverhope and the 

 Moin, and constitute one great series, the age of which is deter- 

 mined both by the order of superposition and by the fossils contained 

 in one of its lower members. 



It is still, however, necessary to call special attention to the upper 

 portion of this group, which, though here and there a quartzose flag- 

 stone, also contains chloritic and micaceous schists, and occasionally 

 exhibits so complete a mineral transition into a gneiss, that Maccul- 

 loch in his map of Scotland, and after him Cunningham, grouped 

 under one name the whole of these superior masses, as well as the 

 great masses now shown to lie below the Cambrian and Lower Silurian 

 rocks. In examining this country in the year 1827, my companion 

 (Sedgwick) and myself distinctly noted both chloritic schist and flat 

 thin-bedded gneiss as occupying several parts of the country, which 

 we walked over in two directions, in the interior of this part of Suther- 

 land ; and we had no doubt that such rocks lay far above the lime- 

 stones of Assynt. That careful and laborious observer, Cunningham, 

 who examined the same tract after a long interval, took the same 

 view. These same overlying rocks are continued, with some undula- 

 tions, from the parallel of Tongue, on the coast, and Ben Clibrig, 

 Lord Reay's Table, and Alt na Harrow, in the interior, to the frontiers 

 of Caithness and Ross-shire on the E. and S.E.* 



Usually thin-bedded and micaceous, they are formed, in certain 

 places, of alternations of greenish- and greyish- coloured micaceous 

 or quartzose gneiss, which present the external aspect of the Italian 

 *' CipoUino" or " onion- coated." Such rocks are seen at the escarp- 

 ment of Ben Hope, in the heart of Sutherland, where they still dip 



* The mountainous fringe extending from near Strathyon the north to Tomen- 

 toul on the south has not yet been examined by me ; and I must abstain from 

 including it in the same category ; for it is by no means impossible that the older 

 gneiss or fundamental rock of the N.W. may there be brought out again. 



