328 Reports and Proceedings — 



the upper series of rocks, the so-called Upper G-neiss, etc. The 

 author, however, found another series of sandstones, calcareous 

 grits, and blue flags beyond the main intrusive mass, and occupying 

 a considerable portion of the gradually descending ground between 

 the river and the heights on each side. These were also penetrated 

 by another arm of the granite, but, as in the case of the limestone, 

 with the sole result of altering them near the junction. Prof. Nicol 

 places a fault at this point, and says that the fundamental gneiss is 

 here brought up to give an appearance of overlying conformably the 

 unaltered series. The author, however, holds, with Sir R. Murcliison 

 and Mr. Greikie, that the next is a younger series, and that it truly 

 overlies the unaltered beds; but he entirely demurs to the view held 

 by them that these should in any way be called gneiss rocks, or 

 associated in any way with beds which have undergone the meta- 

 morphic change so characteristic of the pre-Cambrian rocks as known 

 in this country, and which could only be induced, he believes, by 

 great depression combined with heat, moisture, and pressure. On 

 examination he found these upper beds everywhere unaltered, except 

 near dykes, and the change there induced in them was that now 

 well known as contact-alteration, and which is so entirely distinct 

 from true metamorphism. These beds all dip to the S.E,, and 

 attain a thickness of several thousand feet. They are flag-like 

 in character, are made up chiefly of fragmentary materials, and 

 are occasionally even slightly calcareous. They are much like 

 some of the Lower Silurian flags in Wales, and are in no degree 

 more highly altered than the majority of those rocks, especially 

 in the more disturbed districts. About 3 miles to the east of 

 Glyn Laggan these beds die out, or at least are lost; and the 

 Lewisian rocks, fundamental gneiss, hornblende-schists, and mica- 

 schists, such as those described on the east of Loch Maree, again 

 come to the surface, and the whole of the remainder of the 

 section consists of these last rocks, the great mountains Ben Fyn, 

 Mulart, and others being entirely made up of these rocks without a 

 vestige of the unaltered beds reappearing there. Of the gneiss, 

 hornblende-schists, and mica-schists which compose these moun- 

 tains, it need only be said that, on comparison with others from 

 Loch Maree, Gaerloch, etc., it is impossible to recognize any dif- 

 ference in them, the metamorphism being ia each case identical in 

 character, and garnets and other crystals occur in them in equal 

 abundance. The strike in the beds at Ben Fyn he found also to be 

 almost identical with those on the west coast, the dip being either to 

 the N.E. or E., and seldom, if ever, south of that point. He also 

 found these rocks, and with a similar strike, in the low ground in 

 Glyn Docherty, near the road to Auchnasheen ; and there the 

 Silurian beds are seen resting unconformably upon them. From 

 this the author believes that the Cambrian and Silurian beds are 

 contained in a basin or depression formed of the older rocks, being, 

 however, now altered in their dip and position by slight faults and 

 some folding which has taken place since they were deposited. 



3. " On the Triassic Eocks of Normandy and their Environments." 

 By W. A. E. Ussher, Esq., F.G.S. 



