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7 
Pre-Cambrian Rocks of Ross-shire. 165 
through which heated waters and vapours could have escaped. The 
rocks east of this line, supposed to be newer than any found here, 
but to be far more highly metamorphosed, are in my opinion much 
older than any of these, and to be of Pre-Cambrian age, as I shall 
endeavour to explain more fully further on. 
The prolonged movements which affected the British areas during, 
and which culminated towards the close of the Paleozoic, were 
apparently less in degree here, than in many other areas, and the 
Palzozoic sediments in consequence are less disturbed. Still, the 
unconformities recognizable, and the tilting of the beds (though not 
usually great except near faults), are evidences of these movements. 
These movements, continuous it may be said on a large scale, 
were subject to local interruptions here, as in Wales and elsewhere, 
and breaks in the succession are recognizable in consequence. 
One of these, between the lower conglomerates and sandstone series 
(Lower Cambrian), and the quartz-rocks and limestone series (Lower 
Silurian), is most marked. And I believe it will be found that there 
is another between the latter and the upper flaggy beds (these may 
possibly represent Middle and Upper Silurian). In the Pre-Cambrian 
area along the east side of Glen Laggan, extending up to and dipping 
under the shoulder of the hill, the prevailing rocks are a granitoid 
gneiss and some dark micaceous bands. (Notes 13 and 14.) The 
strike in these as already stated is from N.W. to 8.H., and the angle 
of dip between 70° and 80°. 
[Nore 13.—This rock, although at first recalling to mind a 
graphic granite, does not appear on examination to belong to the 
graphic rocks, granitic or gneissic. It consists of quartz, orthoclase 
and a plagioclase, the little mica which it contains being in exceed- 
ingly thin laminz and colourless. In thin section the quartz and 
felspar are seen to hold the same relations towards each other as in 
the more micaceous gneisses. Individual crystals of felspar are 
frequent, these are plagioclase and microcline. The mica is mono- 
chromatic.—T.D. | 
[Nore 14.—Is a dark bluish-grey, micaceous, foliated rock, very 
close-grained. Magnetite in minute octahedrons is disseminated 
throughout. A microscopic section shows very closely packed folia 
of biotite accompanied with a micro-crystalline mineral which is 
also dichroic, but not to the same extent as the biotite. Between 
these folia lie thickly interspersed the lenticular and banded groups 
of quartz. Sphene is abundant, also magnetite, and a few garnets 
are present.—T.D. | 
The most characteristic of the overlying flagey and schistose rocks, 
with a strike from N.E. to 8.W., especially those which appear to 
have been most highly altered, are described in Notes 15—20. 
[Nore 15.—A compact, siliceous flaggy rock. Under the micro- 
scope shows quartz in rounded or subangular grains distributed in a 
very fine granular mass of the same, with a few fragments of a 
plagioclase. The schistosity here, which is very marked, is produced 
by the abundance of exceedingly minute individual lamin (rarely 
groups) of a monochromatic micaceous mineral, the nature of which 
