Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/481

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471
Dr. Mac Culloch on Quartz Rock.

member among them. In the former notices I have already in some measure described its general aspect and connections, although the limited extent of my researches prevented me at that time from pronouncing decisively as to the latter. I am now, from more recent observations, enabled to confirm the suppositions there made with regard to its place among the older rocks, and to add such a further description of its mineralogical character as to include many more varieties. I shall content myself with merely pointing out its geographic situation in those places which I was prevented from examining more particularly, in the hope that some future observer may direct his attention to them, and ascertain that which I have left undone.

This rock may be seen in Mar accompanying the Dee during part of its course through a country consisting of granite, followed by the usual covering of micaceous and clay slate, a country even in the Wernerian use of the term, primitive. It appears to be stratified, but of its more immediate connexion with the schistus I can say nothing, as I had no means of examining into it. Following the military road which extends from Braemar to Tomantoule it maybe observed in various places, and appears to form the whole or considerable portions of the hills which, declining from the granite ridge of Cairn Gorm, accompany the courses of the Don and the Avon, and are principally constituted of different kinds of schistus. Pursuing this line northwards, it occurs more sparingly, but may still be occasionally observed, together with the schist, till the hills decline into the plain country about Fochabers. I can produce no observations through any part of this course to prove that it is a member of this class of schistose rocks; but from its mineralogical character and general appearance, and from the resemblance which it bears to those quartz rocks whose connexions with the