304 Dr. Mac Culloch on the Geology of Glen Tilt. 



gles 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 Fin- 

 castle, 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 be- 

 tween 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 dis- 

 turbances which I need not repeat. From the river it extends up- 

 wards to a height of many hundred yards in the hill, although not 

 so exposed that we can truly ascertain what alternations it may un- 

 dergo 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. Anthyllis vulneraria, Cistus helianthemum, Satyrium hirci- 

 num, 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 laminse of micaceous or ar- 



