188 MINERALOGY OF THE PENTLAND HILL#. 



It rests Upon the transition rocks of the district/ 

 and occurs in very considerable abundance. It forms 

 the fundamental rockof Turnhouse Hill, Caernethy, 

 East Side Black Hill, the Kipps, Braid Know, 

 Black Hill, Kirk Hill, Castlelaw, the cliffs at 

 Habbie's How ; and nearly the whole of Bald Hill, 

 Mucks Rig, Spittal Hill, and the small hills that 

 extend from West Side to Gaerlips, are composed 

 of this conglomerate. On the south-west end of 

 Black Hill, it is associated with porphyry and fel- 

 spar, apparently in beds ; but of this I am not per- 

 fectly certain, as the cover of debris prevented me 

 examining the relative situation of the rocks with 

 sufficient accuracy. 



II. Sandstone, 



This rock is generally of a reddish-brown co- 

 lour, of different degrees of intensity ; but some 

 varieties, by the action of the weather, become 

 white or grey. It varies from fine to coarse gra- 

 nular, the latter forming a kind of Sandstone Con - 

 glomerate. Its component parts are quartz, fel- 

 spar, clay, and mica ; of these, the quartz is by 

 far the most abundant material. The quartz is of 

 a grey colour, sometimes crystallized, more gene- 

 rally in roundish or angular concretions ; the clay 

 is of a reddish-brown colour, and is the substance 

 which colours the sandstone ; and the mica oc- 



