Pre-Cambrian Rocks of Ross-shire. 105 
far as I can make out from their published statements, been able to 
show conclusively any continuous sections in which these are actually 
seen to repose conformably on the Cambrian rocks, or on the sand- 
stones, limestones, and micaceous flagstones and slates of Silurian 
age. These last, when altered, are partially so only, from actual 
contact with some intrusive rock. Moreover, these Silurian beds 
lie almost invariably at very low angles, usually with a dip from 
10° to 30°, and sometimes they may be said to be horizontal. 
The crystalline schists, on the other hand, which are supposed to 
lie conformably on these unaltered flags and slates, everywhere in the 
eastern, like those in the western areas, lie at high angles, the dip 
being seldom under 50° and usually from 70° to 80°. There is 
generally also a complete discordancy in the strike, when it can be 
traced for any considerable distance. 
The nearer we approach to the earliest history of the globe, the 
more likely are we to meet with similarity of composition in the 
majority of the rocks, and hence it is that though we speak of 
many varieties, yet it will be seen that the minerals which enter 
into their composition are comparatively few, the differences being 
chiefly in the preponderance or otherwise of any of these 
Quartz, felspar, mica, and hornblende are the minerals which 
characterize the majority of the rocks in this area; but chlorite and 
other minerals are also frequently present. Limestone bands also 
occur interstratified with the gneisses at two or three horizons. As 
accessory minerals, garnet, epidote, and sphene are common. Some 
of the rocks consist almost entirely of quartz, others of felspar, or 
mica, or hornblende; but the majority of a varying admixture of 
these minerals. 
On the shore between the Strath Hotel and Gaerloch Kirk a con- 
siderable thickness of very pure mica schists (or slates), with a 
silvery lustre, and containing garnets, occur. They dip at a high 
angle, with a general N.W. strike, and upon their upturned 
edges the Cambrian conglomerates, made up largely of masses 
derived from these and other underlying rocks, lie almost horizon- 
tally. In ascending the hill to the N., a variable series of schists 
and gneiss rocks are seen, dipping regularly upon one another at 
high angles, usually in thin beds, easily separable also into thin 
lamin along the line of bedding, and but very slightly contorted. 
Many are of a dulland some of a light green colour, but the majority 
are red or grey, or consist of thin alternating laminz of these several 
colours. There are very few beds here of the strong gneisses usually 
- found in and supposed to be so characteristic of the western groups ; 
the majority here may be associated more correctly with the chloritic 
and micaceous schistose rocks. Another variety found is a gneiss of 
a bright red colour, due almost entirely to the abundance of minutely 
crystalline garnets present. 
' Collectively the schists found in this and the adjoining mountains, 
on the same line of strike, do not remind one of the usual descrip- 
tions which have been given of the western Pre-Cambrian rocks ; 
but rather of some of those more frequently referred to by authors 
