Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/310

 minute, but well crystallized and dispersed throughout the stone. It is by no means uncommon in similar rocks in Scotland, and occurs, among other places, in Criffel as well as in Braemar; and I may here add, that I have found it in specimens of Egyptian granite which contained no hornblende. I think it unnecessary to enter into any further details of this nature.

It is not far from the granite which I have now described, that the quartz rock with the transition into granite which I have already described, occurs, and it is not necessary to make any further observations on it in this place. At Craig Crocha the granite again makes its appearance; and here, as in other places, it passes by a gentle gradation into syenitic granite, that is, it contains crystals of hornblende.

It is quite superfluous to continue the details of the structure of this ridge with the same minute accuracy, as they will be found little else but a repetition of those which have preceded. It is not however the less important to give a general view of the whole, and I shall therefore state it to as wide a range as is necessary for understanding the structure of Glen Tilt, and the true nature of the interesting appearances there visible.

Ben Dearg may properly be considered as the most conspicuous portion of the granite which forms the basis of this range of hills. It is connected with the right ridge of Glen Tilt which I have now been describing, by a succession of granite and quartz rock, exactly similar to that already noticed. Pursuing the direction of the country across the Tarff to Cairnmuir and the head of Dee, the same succession gradually unites the granite of this tract to that which forms Cairngorm and Ben Avon, the great central granite of the Grampian hills, and the most extensive tract of this rock in Scotland.

There is no reason then to doubt that the granite which forms the