194 GEOLOGY OF ARRAX. 



syenites, the same as those which succeed the granite on its 

 west border (Art. 11), strike in upon the road, intermingled 

 with sandstone, here of carboniferous age. The bottom of 

 the glen and steep ridge on the right are composed of the 

 old red sandstone. The old bridle path runs at the base of 

 this ridge. On its smooth outline it is curious to notice 

 watercourses and glens in an absolutely initial stage; such 

 is the force due to the height of descent, that water 

 collected into the merest rill, by the slightest possible 

 inclination, has a great power of excavation, and speedily 

 forms a perceptible channel and considerable talus. Leaving 

 the high road at the Glen Loig bridge we shall find a bed 

 of limestone high on the southern hill-side, by following a 

 bridle road leading up to an old quarry. It is a crystalline 

 limestone without fossils, much altered by trap veins which 

 traverse it, and to which the rock adheres firmly. It 

 seems to be near the base of the carboniferous series, in 

 the same position as the limestone at Achab farm and the 

 Fallen Rocks. 



"We are now close upon the Craig-Dhu granite, already 

 fully described (Art. 12). Craig-Dhu is a high steep cliff, 

 fronting that part of the Shiskin road where the Dougrie 

 road parts off from it. A talus of blocks strews its base (see 

 Art. 12). 



A little farther forward, opposite the pillar letter-box, the 

 Dougrie road turns off to the right, crossing Mauchrie Water 

 by a substantial bridge, and passing through the stunted 

 remains of an old forest; the distance is about three miles. 

 The only house on this road is the farm-house of Mauchrie, 

 opposite to which a path leads down to a wooden footway 

 across the stream and near the shore by which we can easily 

 reach the Toruiore pitchstones. The stone circles, a mile 

 inland, and due S. of the farm-house, may also be reached 

 this way by a very short route. But we shall visit them 

 from the shore. 



From the wayside post-office we continue our course to 



