iHlNERALOGY OF THE PEKTLAND HILLS. 193 



appears to be composed of rolled masses of porphy- 

 ry or clinkstone, contained in a porphyritic basis ; 

 but these masses are to be observed passing by im- 

 perceptible degrees into the basis, and hence are 

 of cotemporaneous formation with it, and cannot 

 be viewed as fragments. 



This rock rests upon the conglomerate ; but its 

 immediate relation to the red sandscone, I had no 

 opportunity of ascertaining. It occurs very abun- 

 dantly throughout theMid-Lothianpartof the Pent- 

 lands, but more frequently in the middle part, and 

 the eastern extremity, than in the western. It ap- 

 pears in general rather on a low level, near the foot 

 of the hills ; although in particular instances j as at 

 the Kipps and the Kirkyetten Ilills, it forms 

 summits upwards of a thousand feet high. 



On the outside of the group, it extends from 

 East Side to Kirkyetten^ and onwards to Malleny, 

 forming a nearly continuous mass. The smaller 

 hills that skirt the group in this line of direction, 

 are also composed of it ; and it is to be seen in the 

 interior of the group in the Logan Water valley, 

 at the foot of Turnhouse, Caernethy, and Castle- 

 law Hills, where it rests upon conglomerate ; and 

 fine sections of it are exposed oa both sides of 

 Glencross. 



VOL. II* 



