Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/135

 mountains. I do not mean to say that this is likely to prove general, but I merely point it out as an accompanying circumstance, to be confirmed, or perhaps contradicted, by future and more numerous observations.

Having thus determined the nature of Cruachan itself, it will be useful to trace its connection with the surrounding mountains, and in defect of more satisfactory observations, to conjecture by their external aspect and by analogy, the nature of their composition. It forms the highest point of a complicated group, which to the south-east is bounded by Loch Awe, to the south-west by Mid Lorn, and to the north-west by Loch Etive, but which extends towards the north-east in a continuous line, uniting itself with the ridges of Schihallien and Ben Lawers. The part of this group which the great elevation of Cruachan brings almost immediately under the eye, is coextensive on the three quarters first enumerated with the boundaries there mentioned. To the north it does not extend further than Buachaille Etive, while it is in some measure separated from the eastern mountains by the lower land of the Black Mount over which the military road passes. Within this space the whole of the mountains, including both boundaries of Loch Etive, appear to consist of granite, and to be of the same composition with Cruachan; there being no perceptible difference either to the naked eye, or when seen through the telescope, between their general outline, fracture, mode of disintegration, colour, or form. How far this conjecture may be confirmed by actual examination, or to what extent they may resemble it in the minor circumstances, the intersections of porphyritic veins, can only be known by inspection of the rocks themselves, a task not likely to be soon accomplished, since it is scarcely possible to discover a mode of traversing this