Pre-Cambrian Rocks of Ross-shire. 223 
limestone group was altogether absent, whilst in others this would 
be seen to spread out perhaps to a great thickness, and from all the 
evidence that has been collected this seems to be very much the case. 
Moreover, there are some indications also of an actual overlapping 
of the limestone beds by some flaggy sandstones towards the upper 
end of Glen Laggan, along the west side; but further examination 
is necessary before this can be accurately ascertained. In Section II. 
the unconformity between the series f and the sandstone below is 
tolerably well marked. 
The rocks examined, belonging to groups e and f, seem to be 
about equally altered along this line, being most so when in contact 
with igneous dykes, or faults; and scarcely at all, or not more so 
than is usual in rocks of Silurian age in other areas, when unaffected 
by these causes. 
Along the east side of Glen Laggan the groups e and f are seen 
at several places to rest upon the upturned edges of the Pre- 
Cambrian. rocks. The latter composed mainly of granitoid gneiss 
and dark mica schists, as described in Notes 13 and 14. These strike 
from N.W. to §.E., and are therefore entirely discordant to those 
which repose upon them. This same discordance in the strike of 
the beds, and difference in mineralogical characters, may be traced 
eastward in Glen Docherty, with but slight interruptions only from 
want of exposures, for several miles. The lower rocks everywhere 
a highly metamorphic group, with a high dip and a strike from 
N.W. to §.E.; and the upper unequally altered, never for any 
distance truly metamorphic, and always at a low angle, and with a 
strike from N.E. to 8.W. Towards the upper end of the Glen the 
lower rocks are seen to ascend to a considerable elevation, and are 
there cut through by the road where it begins to descend into the 
Glen. These lower rocks at this point consist chiefly of reddish 
highly felspathic gneisses, described in Notes 21 and 22. 
[Nor 21.—Is macroscopically exceedingly fine-grained, almost 
compact, of a reddish colour, consisting of felspar, and shows no 
indications of foliation. The microscope shows that it is composed of 
closely developed crystals of felspar, almost wholly orthoclase, which 
is much decomposed ; the interspaces, which are small, being occupied 
with quartz and calcite. The latter also fills fissures, and is of 
secondary origin. No mica is present, unless a yellowish-grey nearly 
opaque substance may be regarded as representing this mineral. 
A pale-coloured garnet, in very small crystals, is scattered through- 
out. Indications of a tendency to a foliated structure, though not 
striking, are not wanting.—T.D. 
[Nore 22.—A fine-grained rock, of a reddish colour, with much 
red felspar and a colourless mica. 
“A thin section discloses intimately crystalline quartz in wavy 
bands, with much decomposed felspar, which is principally ortho- 
clase. The colourless muscovite, thoagh occasionally in fairly 
continuous bands, is also generally distributed in isolated lamina, 
1 Tt is however too strongly indicated in the section, and carried up too high into 
the cliff. 
