234 Geological Soctety.:— 
cerned; but differs from him in maintaining that there is no upper 
series of quartzite and limestone, and that there is no evidence of an 
‘* upward conformable succession’’ from the quartzite and limestone 
into the eastern mica-slate or gneiss—the o-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. ‘his 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 succession” above referred 
to. Im 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 eruptive 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 west coast, and brought up by a 
powerful fault along a nearly north and south line passing from 
Whiten Head (Loch Erriboll) to Loch Carron and the Sound of Sleat, 
are chiefly those which had been brought forward as affording 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 conformable succession.” 
Prof. Nicol 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 toa 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 been insisted upon, that the strike of the western gneiss is dif- 
ferent from that of the east; but the author remarks that the strike 
is not persistent in either area, and that great movements subse- 
quent to the deposition of the quartzite series have irregularly affected 
the whole region. With regard to mineralogical characters, Prof. 
Nicol insists that both the eastern and the western gneiss are essen- 
tially the same. Both are locally modified with granitic and horn- 
blendic matter near igneous foci ; but no proof of a difference of age 
in the two can be obtained therefrom. The alteration in bulk of the 
gneiss in the western area, by the intrusion of the vast quantities of 
granite now observable in it, may perhaps have caused the great 
amount of crumpling and faulting along the N. and S. line of fault, 
dividing the western from the eastern gneiss,—a fault comparable 
with and parallel to that running from the Moray Firth to the Linnhe 
Loch, and to the one passing along the south side of the Grampians. 
