Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/483

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473
Dr. Mac Culloch on Quartz Rock.

the correlative of secondary, and involves no hypothesis with regard to the absolute æras of rock formations. But I must pass on to further matter of fact, leaving to the labours of future geologists, the actual connections and origin of these breccias, and the distinctions to be drawn among this very intricate class of rocks.

In the district of Appin the quartz rock may be observed in various parts, and although I have not been able in this place any more than in Mar, sufficiently to trace its connexion with the mica slate of the country, I have little doubt that it immediately follows, and possibly alternates with it. It may be seen not far from the castle of Bercaldine, and forms a large detached rock at Airds. Here it is of a highly indurated character, and bears the marks of a disturbed stratification. I do not think it necessary to describe the particular aspect which each rock assumes, as it most frequently happens that various modifications of it are to be met with in the same spot, and I prefer delaying the general description till I have mentioned the several places in which it is found.

The same rock occurs in the district of Arisaig. It occupies there a considerable portion of the shore, and may be traced forming low hills and interrupted projections, from the point of Arisaig, nearly to Loch Morrer. It seems here to alternate with mica slate, as I have already mentioned in another place, where I have quoted Professor Playfair's remarks on it; but possesses much less of the appearance of stratification than in the other instances which I have enumerated.

In the island of Sky it occupies a considerable space, and forms that large mountain mass which projects from the general eastern boundary of the island, so as to produce, together with the main land, the narrow passage of the [1]Kyle rea. Here it assumes a

  1. Kyle rea the smooth strait, Kyle ree the King's strait, but both are corrupt etymologies. Kyle rich, the swift strait.

Vol. II.3 o