Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/474

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Dr. Mac Culloch on Quartz Rock.

and other varieties of primitive schist.” Since this paper was originally drawn up, I have seen the country he here quotes, (Arisaik) and have confirmed that his “granitic sandstone” is the rock which I have been describing, and that it is the same rock which he has also described as constituting the ridge of Schihallien, a place of which I shall presently have occasion to speak. Possibly these authors, impressed with the notion that this rock was as “granular quartz,” and that granular quartz was a primitive rock, have not thought it necessary to push their investigations as far as they might have done, nor made the important deductions which must needs follow from this fact if proved. On the geological consequences which would result from its being established it would be useless to speculate till the fact be fully ascertained, as I trust it will be in the sequel of this paper, but it is obvious that it would occasion the removal of mica slate out of the chemical deposits of the Wernerian system, and place it among the mechanical, or at least the mixed ones: a change which seems to be called for by many other circumstances attending the formation of mica slate. But I must leave this part of the subject for future consideration.

The true nature of this rock being now, as I trust made out with regard to Jura and the western part of Sutherlandshire, we are next led to inquire what evidence there is to prove that all the mountains of “granular quartz” are not of a similar nature, and do not belong to some of the ancient recomposed rocks. The mountains of Scuraben and Morven are cursorily described by Jameson, the former as having a summit of quartz, the latter as possessing the peculiar white aspect so characteristic of the hill. I have noticed on the western coast and in his work on Geognosy, they are actually quoted as examples of quartz rock. Mr. Pennant