Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/312

 to the stream, a succession of limestone continuous with that at Gow's bridge before described is found to a considerable height in the hill. It will be useful to point out the general bearing of this great range of limestone. It crosses the hills at Lude, tending towards the south, whence it passes through the Glen of Fincastle, and across the valley of the Tumel. Limestone is again seen at Mount Alexander, and at the base of Schihallien, from whence it appears to proceed through Glen Lyon to the side of Loch Tay; but I have not been able to trace any connection between these detached places. Eastward it extends by the side of the Scarsough to Mar, beyond which point I am unacquainted with the country.

To examine it more particularly. From Gow's bridge up the course of the Tilt to Forest Lodge it is seen skirting the banks of the river, and alternating with schist and quartz rock, while in the places formerly described it joins the granite, and undergoes those disturbances which I need not repeat. From the river it extends upwards to a height of many hundred yards in the hill, although not so exposed that we can truly ascertain what alternations it may undergo through this space. Every where its course is marked by the most lively verdure, forming a strong contrast with the brown and barren aspect of those hills where the subsoil is granite or quartz rock. Authyllis vulneraria, Cistus helianthemum, Satyrium hircinum, and other plants which affect calcareous soils, are found on the faces of these green hills.

This limestone is of a blueish colour, and almost always of a large grained fracture. Where it lies in contact with quartz rock, it is commonly of a harder texture than in more distant portions, and where it is about to alternate with schist it is often interfoliated with thin lamina of micaceous or argillaceous