146 



THE GEOLOGIST. 



tlie matured results of his observations. He agrees with Sir R. Murchison as 

 far as the succession of the western gneiss, red sandstone, quartzites, (quartzite 

 and fucoid bed), and limestone is concerned ; but differs from him in maintaining 

 that there is no upper series of an " upward conformable succession" from the 

 quartzite and limestone into the eastern mica-slate or gneiss — the so-called 

 "upper gneiss." The "upper quartzite" and "upper limestone" the author 

 believes to be portions of the quartzite of the country, in some cases separated 

 by anticlines and faults and cropping out in the higher ground, and in other 

 instances inverted beds with the gneiss brought up by a contiguous fault and 

 overhanging them. The latter condition of the strata, as well as other cases 

 where the eastern gneiss is brought up against the quartzite series, have, 

 according to the author, given rise to the supposed " upward conformable suc- 

 cession" above referred to. In some cases where " gneiss" is said to have been 

 observed overlying the quartzite, Professor Nicol has determined that the 

 overlying rock is granulite or other irruptive rock, not gneiss. 



The sections described by the author in support of his views of the eastern 

 gneiss not overlying the quartzite and limestone, but being the same as the gneiss 

 of the western coast, and brought up by a powerful fault along a nearly north 

 and soutli line passing from White Head (Loch Emboli) to Loch Carron and 

 the Sound of Sleat, are chiefly those which had been brought forward as afford- 

 ing the proofs on which the opposite hypothesis is founded ; and in all, the 

 author finds irruptions of igneous rocks, and other indications of faults and 

 disturbance, depriving them, in his opinion, of all weight as evidence of a 

 regular order of "upward and conformable succession." 



Prof. Nichol further argues that the mode of the distribution of the rocks 

 shows that there is through Sutherland and Ross-shire a real fault, and no 

 overlap of eastern gneiss of more than a few feet or yards at most; and that the 

 fact of different strata of the quartzite series being brought against the gneiss 

 at different places supports this view, and points to a great denudation having 

 taken place along the line of fault. Though the quartzite is here and there 

 altered by the igneous rocks, yet it is truly a sedimentary rock, and so is the 

 limestone ; but the eastern gneiss or mica-schist is a crystalline rock throughout. 

 This fact, according to the author, is inimical to the hypothesis of the eastern 

 gneiss overlying the limestone and quartzite. It has b'een insisted upon, that 

 the strike of the Avestern gneiss is different from that of the east; but the author 

 remarks that the strike is not persistent in either area, and that the great 

 movements subsequent to the deposition of the quartzite series have irregularly 

 affected the whole region. With regard to mineralogical characters, Professor 

 Nichol insists that both the eastern and western gneiss are essentially the same. 

 Both are locally modified with granitic and hornblendic matter near igneous foci: 

 but no proof of difference of age in the two can be obtained therefrom. The 

 alteration m bulk of the gneiss in the western area, by the intrusion of vast 

 quantities of granite now observable in it, may perhaps~have caused the great 

 amount of crumpling aud faulting along the" north and south line of fault, 

 dividing the western from the eastern gneiss,— a fault comparable with and 

 and parallel to that running from the Moray Frith to the Linhe Loch, and to 

 the one passing along the soutli side of the Grampians. 



December 19, I860.— 1. "On the Geological Structure of the South-west 

 Highlands of Scotland." By T. P. Jamieson, Esq. 



In this paper the author attempts to throw light on the relations of those 

 rocks which figure in geological maps as the mica-schist, clay-slate, the chlorite- 

 slates, and the quartz-rock of the soiith.western Highlands,' which range north- 

 east through the middle of Scotland, forming an important feature in the 

 geology of that country. An examination of these rocks, as displayed in Bute 

 and Argyleshire, has led Mr. Jamieson to believe that, from the quartz-rock of 



