40 
Proceedings of Royal Society of Edinburgh. [sess. 
sometimes even one single mountain, may present the whole of them 
to the eye in a splendid succession of precipices and of slopes. The 
general or normal order in that succession is exhibited in many 
of the finest hills. At the base there is that peculiar gneiss, 
which no geologist who has ever seen it can again mistake — 
sometimes called Hornblendic, from one of its most characteristic 
minerals — sometimes Laurentian, from its immense local develop- 
ment on the northern shores of the St Laurence — and more 
recently termed the Archaean, from its being the oldest sedimentary 
deposit as yet known in the world. On the top of this very 
ancient rock — with all the marks and aspect of a most hoar antiquity 
on its face — there rise immense, but isolated and broken masses of a 
deep chocolate-red sandstone supposed to be of Cambrian age — 
sometimes in low hills or sloping promontories, but more generally 
in fine mountains of very peculiar and very steep and sudden 
outlines — each separated from its nearest neighbour by deep 
glens or arms of the sea, or lakes of fresh water — and each 
looking as if it had come there by some inexplicable accident, 
seeing that it bears no obvious relation to the other rocks 
upon which it sits, or to the general aspect of the country out 
of which it rises. Then, lastly, in some places, but not every- 
where, on the top of these steep and violent mountain forms — cut 
out, as it would seem, from some greater mass which has been 
swept away — we have a cap or summit composed of a pure white 
quartzite beautifully stratified — sometimes grey with lichens and 
mosses, but very often also unstained and glittering, like mountains 
whitened by an early fall of snow. The stratification of this 
quartzite is always unconformable with that of the red sandstone 
on which it lies, and as those mountains are all nearly naked of 
vegetation at the top, the difference in the lines of bedding is 
almost as conspicuous to the eye as the difference in colouring 
between the two rocks. 
The lowest of these three great rock masses, which is the floor 
or basement rock along the whole of the west coast of Sutherland, — 
although in Canada it has furnished certain bodies which have been 
supposed to be, and probably are, of organic origin, — the so-called 
Eozoon,— has not yet in Scotland supplied even a doubtful indica- 
tion of animal or of vegetable life. It is, so far as yet observed, 
