158 Wessrs. Hicks and Davies— 
disturbing the strike of the overlying rocks, than accept so simple 
an interpretation. These are, however, matched in their dream of 
possibilities by those who have suggested that the overlying rocks 
have, by some process of twisting, or sliding, been made to reappear 
below in the character of the old rocks, with a strike there at 
right-angles to themselves, and a nearly vertical dip, and this for a 
distance of several miles. Possibly the very palpable difference 
between a conglomerate and the underlying rocks may have prevented 
any such idea being entertained in the more immediate neighbour- 
hood of Loch Maree. Otherwise, had the overlying rocks been made 
up of finer materials, and yet derived from the same sources— 
detrital from gneisses, granitic and felspathic rocks, and hornblende 
and mica-schists—the case might have been different, and by some 
powerful stretch of the imagination such a result might even here 
have been thought possible. That some of the overlying rocks do 
occasionally simulate those from which they have been derived is 
well known, and the following remarks on the lower beds of the 
conglomerate series by Prof. Nicol are instructive on this point :! 
“Fragments of gneiss and granite are baked up in the mud of 
decomposed felspars, mica and peroxide of iron. The deeper beds 
are frequently purplish brown; the higher, darker or bright red. 
The lower portion too near the sources of heat are hardened and 
compacted almost like the gneiss or granite out of which they were 
made. Sometimes they have even been mistaken for gneiss.” 
Detached crystals and fragments of felspar, hornblende, garnet, ete., 
are also very commonly present in the finer sediments, and the 
admixture of these is sometimes so complete, that at first sight one 
may be led to think that the rock was truly crystalline. This, 
however, can generally only occur in small specimens, for, when a 
mass of any size is examined, larger fragments with irregular out- 
lines are visible, and the brecciated character of the whole is easily 
made out. This curious crystalline appearance sometimes assumed 
by the Cambrian rocks is due in a great measure to the very slight 
amount of attrition to which the materials composing them have 
been subjected, and to their having been derived primarily from 
crystalline rocks. Bits of vein quartz and granite, in addition to 
fragments of the schists, or of some of their crystalline constituents, 
compose nearly the whole of these Cambrian conglomerates and 
sandstones. Scarcely any decomposition comparatively of the 
various minerals had by this time taken place, and organic 
life had added but little to the sediments; hence the ordinary 
results of decomposition, the muddy and other deposits found in 
more recent strata, are here nearly altogether absent. These Lower 
Cambrian rocks are followed, on both shores of the lake, by 
quartzites, usually made up of very minute grains. These rest 
unconformably upon the former, and evidently therefore belong 
geologically to a newer formation ; whether of Upper Cambrian or - 
of early Silurian date is at present doubtful. On the north-east shore, 
nearly at the eastern end of the lake (Section II.), a fault is seen 
* The Geology and Scenery of the North of Scotland, 1866, p. 28. 
