DESCRIPTION OF TINTO. 



129 



tb stretch beneath a gradually descending line to 

 the eastern extremity of the base. At this ex- 

 tremity, and at a small height above the kvei 

 ground, we observe the commencement of ihb 

 cilay stone and felspar formation, which lies over 

 the conglomerate and greenstone rocks, and by 

 means of the reddish-coloured debris, above the 

 line now mentioned, may be traced westward, 

 along the brow and rounded back, to the summit 

 of the mountain, forming the whole of its upper 

 part. The claystone passes into felspar, and oc- 

 casionally presents dendritic delineations and veins 

 of heavy-spar. I am inclined to think» that be- 

 twixt the conglomerate and the claystone, there 

 is all along interposed a mass or bed of the green- 

 stone substance which appears in the Pap-Cragg, 

 and which, here, might be supposed as in fact no- 

 thing else than the base of the conglomerate un- 

 mixed with the coarser fragments that occur to- 

 wards the lower part of the base : but I had no 

 opportunity of verifying the conjecture. 



On the dechvity of Tinto, towards the north 

 and north-west, similar substances occur : but the 

 felspar formation descends considerably lower 

 down than under the south side of the summit. 

 The body of the mountain on the north side, is 

 indented by three deep re-entering angles, and 

 presents two vast projecting shoulders, one facing 

 the north, the other inclining to north-west. These 

 shoulders are evidently covered with the porphy- 

 ry formation which compo-^es the summit, and ex ■ 



