Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/196

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are engaged in investigating the irregular ones. The whole of the original remarks on this quarry must therefore be obliterated from the record.

There yet remain with respect to the trap rocks of Sky many facts which have resulted from the later more extended examination I bestowed on them. But as these would lead into details inconsistent with the purposes of this paper, and as they are important rather in a general view than as illustrating the history of that island, I shall reserve them for some future communication.

Having thus made the additions and corrections which appeared of most importance in the geological history of Sky, I shall proceed to enumerate some minerals which were either entirely omitted or but imperfectly seen.

In the small island of Oransa, and still more conspicuously in an islet adjoining to it, there is to be found a mass of actinolite rock, which can also be traced to the adjoining shore of Sky near to Camiscross. It lies among the gneiss, holding an uniform and parallel course with it, and as the beds of gneiss are here nearly vertical, it presents the appearance of a vein, its edge alone being visible. Nevertheless, its conformity with the gneiss, the analogy which it bears to common hornblende-schist, and its actual gradation into that substance, leave no doubt respecting its true character. The edge of this bed is very irregular, as the bed itself is interrupted and split in various places by intruding laminæ of gneiss, thus contracting in some places to the breadth of two or three inches, and again enlarging to that of as many feet. It is formed of a confused crystallization of actinolite of a pale green colour, the crystals being almost always very minute, and so entangled that the fracture often appears as much granular as it does schistose. It does not present those varieties which occur in the well known rock of Glen Elg,