Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/475

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465
Dr. Mac Culloch on Quartz Rock.

too, although not an authority in a case of this nature, describes quartz about Loch Broom, and more cursory observers have given us reason to think that the generality of the higher mountains of this northern tract of Scotland are composed of “quartz.” There is little doubt that the whole of this elevated tract is of the same formation as that under consideration, and it ought therefore perhaps (according to the remarks I have already made on Jura) to be ranked with the Transition rocks, if we adopt the divisions of Werner.

If this be proved it will be highly interesting to ascertain the positions of all the strata throughout this whole district. Of the unstratified rocks it will always be difficult to determine what portion has been removed, or what changes of the original position may have taken place, as we have no guide to conduct us in our judgment, ignorant as we must generally remain of their original forms. With the stratified rocks the case is otherwise, their existing forms furnishing us with a palpable index, by which we may discover either the changes of position they have suffered, or the waste they have undergone. Certainly the north-west coast of Scotland gives evidence of an enormous waste of the surface, and opens an ample field for the speculations of those who have attempted to assign the causes of that waste: to them I must at present leave it.

I have already, at the beginning of this paper, remarked the similarity which the outline of the mountains of Sutherlandshire bears to that of the Wicklow mountains. These, in the paper of Dr. Fitton, above mentioned, are also called granular quartz. As I have neither seen the mountains themselves, nor any specimens from them, I am unable to decide whether they are actually similar in structure and geological character to the Scottish quartz mountains,

Vol. II.3 n