Pre-Cambrian Rocks of Ross-shire. 267 
no doubt whatever that the interpretations supplied by Ben Fin and 
Mulart are equally applicable to those portions of the range. 
In my former paper I described the rocks composing these 
mountains as “a highly crystalline series, chiefly gneiss with 
garnets, mica schists also with an abundance of garnets, and some 
hornblende schists”; and that “the crystallization is in no way 
local, but affects the whole series equally; and it is that form so 
peculiarly characteristic of the older or Pre-Cambrian rocks wherever 
they are exposed in this country.” 
I devoted a considerable time to the examination of these moun- 
tains, and collected specimens at all horizons as far as this was 
possible. It is perfectly clear that the vertical thickness of the 
rocks exposed is very great, but there are distinct evidences also of 
their being frequently repeated in minor folds. Amongst the speci- 
mens collected may be specially mentioned the following varieties :— 
1. A rather massive gneiss, consisting of thick bands of coarse- 
grained white and pink felspar, with quartz, and lamine of black 
and white mica with garnets and sphene. 
2. A gneiss in which the orthoclase felspar is frequently developed 
in well-defined crystalline groups, with black and white mica and 
garnets in large distinct crystals. An augen-gneiss. 
3. A coarse-grained granitoid gneiss, with garnets and sphene. 
4. A fine-grained ditto ditto. 
5. A coarse granite, with large flakes of mica (probably a vein). 
6. A dull-coloured mica schist, with an abundance of decomposing 
garnets, giving to the whole a rusty appearance. 
7. Bright silvery mica schist, with garnets. 
8. A highly micaceous gneiss, consisting of bands of white and 
black mica, with a moderate amount of quartz and felspar, and some 
garnets and sphene. 
9. A medium-grained hornblende gneiss, with much sphene.! 
10. A massive hornblende rock, coarse-grained, with much sphene. 
Several of the above are more fully described by Mr. Davies in 
Notes 25-28. 
[Nore 23.—This rock appears to be a fine-grained foliated gneiss, 
in which the orthoclase occasionally occurs as large crystals or lenti- 
cular groups of crystals, forming the variety called augen-gneiss. A 
thin section shows that quartz is the predominant mineral. ._Much 
of it is very intimately crystalline, and in lengthened-out grains 
according with the direction of the foliation. The grains are only 
individualized when seen between crossed Nicols. The quartz is 
very clear, though in some bands there are numerous grains which 
1 Professor Bonney in his paper (Quart. Journ. Geol. Soc. vol. xxxvi. p. 105) 
says that he ‘‘ failed to find any hornblendic rock other than intrusive’’ in Ben Fin. 
That Nos. 9 and 10 are not intrusive is in my opinion (as also in Mr. Davies's) almost 
beyond doubt, and I am surprised that Prof. Bonney did not meet with them, espe- 
cially as he appears to have come across, at an horizon near where these are found, 
what he calls a ‘‘garnetiferous diorite.’’ That, however, he should not have touched all 
the varieties in his hurried examination of a few hours is not at all surprising, consider- 
ing that I spent two whole days on these mountains, and had even then to miss many 
points. 
