Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/139

 at 24 miles, with no variation of character; but of its breadth between north and south I am unable to speak, the country being absolutely trackless and uninhabited.

It appears to me however that it extends, perhaps with some interruption, from the schistose rocks to Ben Vualach by which it is connected with the granite district of Loch Ericht; and there is equal reason to suspect that to the westward of this it will be found similarly connected with the granite of Ben Nevis.

Where it terminates, at the head of Loch Rannoch, it forms hills of moderate elevation, and these are immediately followed and covered by a succession of schistose rocks, consisting of quartz rock, micaceous schist, and an obscure variety of gneiss which I have already had occasion to describe in another place. The junction of the two may be observed in different places, in all of which it is invariably accompanied by the appearances already noticed at Balahulish, namely, fragments of the different schists imbedded in the granite.

The schist which is here imbedded in the granite is often composed of black scaly mica with a high lustre. Towards the junction of the fragment with the surrounding rock it generally contains crystals of hornblende. The fragments vary much in size, and I must add that they differ completely in aspect from those accumulated plates of mica which are found in the granite of Aberdeen, as well as in many other granites. In other cases the imbedded fragments consist of the same quartz rock and gneiss which form the general body of these schistose rocks. If any mineralogists are unwilling to consider them as imbedded fragments, it can only be said that if they were really detached fragments they could possess no other aspect than that which they now have. The head of Loch Spey,