20 



Me. J. BuTCE on the Discoveiy 



so frequented as this, the occurrence of the granite had so long 

 remained unnoticed. On an early subsequent visit, I determined the 

 limits of the tract to which the rock is confined. The annexed ideal 

 section, from east to west, between Corriegills and Mauchrie water, 

 represents the position and relations of this granite tract, as well as 

 that of Ploverfield, the horizontal extent of the sandstone being of 

 course much contracted : — 



(a) Granite of Phverfield ; (li) new granite tract at Craig-Dhu ; (e) old red sand- 

 stone of Mauchrie water; (d) sandstone with heds of limestone, the whole of car- 

 boniferous age ; (e) eruptive rocks of Doir-nan-Each, the highest hill in the west district 

 of the south section of the island, chiefly porphyry and highly liornblendic basalts. 



The granite tract now to be described lies on the south side of the 

 Shiskin road, nearly opposite the farm house of Glaister. Here the 

 hill, whose base is sku-ted by the road all the way down from the 

 " String," overhangs the valley of Mauchrie water in a steep cUff called 

 Craigmore, Craig-Dhu, or The Corby's Rock. This cUff is the outer 

 edge of a small plateau or table land, cut off from the higher ground 

 behind, towards Dou--nan-Each, by a deep hoUow which completely 

 isolates it. The summit is 700 to 800 feet above the valley, and is 

 more than a quarter of a mile long, by one to one and a-half furlongs 

 broad. It descends steeply towards Shiskin on the south-west, and 

 slopes gradually north-east towards Moniquail. The summit and sides 

 of this plateau are formed of fine-grained granite, ver^^ similar to that of 

 Ploverfield. The base of the cHff towards Mauchrie water is covered 

 by a long talus of granite blocks and smaller fragments, reaching to 

 within 200 or 300 yards of the road, and appeai-iug even at that dis- 

 tance of very different aspect from fallen masses of sandstone. 



The granite here seems to rise either through the old red sandstone, 

 or at the junction of this rock with the carboniferous strata. The 

 granite is nowhere seen in situ at a low level ; the talus before men- 

 tioned obscures the rocks along the base of the hill, and the ground 

 by the roadside, and along the valley, is deeply covered with alluvium. 

 At one spot only could we detect any rock in situ. Immediately below 

 the bridge, by which the road crosses a small stream, the water runs 

 over a projecting mass, which seems to be either a serpentine, a 

 greenstone with much felspai*, or an iron-shot claystone. But at a 

 high level on the west, south, and east sides of the plateau, the granite 

 is seen to rise through a coarse conglomerate ; and numerous contacts 



