MINERALOGY OF THE PENTLAND HILLS. 185 



III. Greenstone. 



This rock presents the usual characters of green- 

 stone. It occurs in beds sometimes twelve feet 

 and upwards in thickness, situated in clay-slate. 

 Neither the greenstone nor clay-slate, where in 

 contact with each other, appear altered or inter- 

 mixed. Two beds of this rock occur in a quarry 

 of clay-slate above Bevelaw-House^ 



IV. Porphyry, 



Upon the north-eastern extremity of the Black 

 Hill, where the transition clay-slate occurs, fel- 

 spar-porphyry and felspar-rock make their appear- 

 ance and these are so connected with the clay - 

 slate, that I cannot help suspecting portions of 

 these rocks may here belong to the transition 

 series* 



Section IV. 

 flcetz rocks. 



The floetz rocks, of which by far the greatest 

 part of this portion of the group is composed, 

 Sire the following : Conglomerate, Sandstone, 



