160 Messrs. Hicks and Davies— 
cutting across, though yet apparently in the line of strike of the last- 
mentioned rocks, dropping them to a lower horizon towards the 
S.E. The floor of Pre-Cambrian rocks, observed to be gradually 
sloping from the west towards this point, is further dropped also by 
this fault, and its continuity broken by an intrusion of the igneous 
rock described in Note 9. 
[Norz 9.—A macroscopic examination exhibits a compact felsitic 
base, grey to pinkish grey, in which is thickly distributed a horn- 
blende-like mineral in crystalline spots and patches. When a thin 
section is examined, it is found to consist very largely of a dark-green 
mineral, which is rendered very obscure by the amount of alteration 
which the whole rock has undergone. It is very slightly dichroic. 
The habit, however, of a considerable part of it is so like that of 
hypersthene that I am disposed to refer it to that species for the 
present. The felspar is entirely decomposed, small spaces and 
interstices being occupied by a little calcite and secondary quartz. 
I regard this rock as a much altered hypersthenite. It is undoubtedly 
intrusive, and has nothing in common with the hornblende gneisses. 
—T.D. 
In former paper this mass was described as syenite. Mr. 
Davies now calls it a quartz diorite. Whether this mass directly 
beyond the fault extends continuously under the sedimentary 
rocks to reach a similar mass met with in the centre of Glen Lage gan, 
Iam unable to say. In any case they are sufficiently identical in 
character to be soassociated. The largest exposure in Glen Laggan, 
from where the specimen actually described was collected, is seen on 
the sides of the river about a mile and half from the entrance to 
the Glen (Section III.). In its immediate neighbourhood the rocks 
are twisted and crushed, and also altered considerably. In the line 
of Section II. (which is taken along the Kenloch Ewe heights, 
and across the entrance of Glen Laggan), in the cliff immediately 
opposite Kenloch Ewe, a mass of rock is seen of a granitic type, 
but whether intrusive into the newer rocks like the quartz diorite is 
at present doubtful. It is described by Mr. Davies in his Note 10. 
| Norz 10.—This is a coarse granitic rock in contact with a vein 
of a hard, compact, pale yellowish-green substance. Microscopically 
we find coarsely crystalline orthoclase with plagioclase in nearly 
equal proportions, and quartz, the whole being pervaded with a 
microscopic dust which is more conspicuous in the felspars. No 
mica is visible. Jt differs from the gneisses generally in the more 
intimate crystallization of its minerals. The vein substance varies 
from crypto- to micro-crystalline, is doubly refracting, and, judging 
from its resemblance and the similarity in its mode of occurrence to 
that of the island of Iona, which has been shown by analysis to be a 
lime epidote, is to be referred to that species.'| It contains much 
angular quartz, probably derived from the granitic rock, and is in 
places much crushed, so as to resemble a breccia. Smaller veins and 
patches of the same pervade the mass.—T.D. | 
1 Mineralogical Notices by Prof. N. S. Mabkelyne and Dr, W. Flight, Journal 
of the Chemical Society, Jan. 1871. 
