130 



DESCRIPTION OF TINTO. 



tends ovet the eastern acclivity and ridge of the 

 mountain ; but underneath it, the same rocks, 

 claystone, porphyry-slate, and conglomerate, with 

 the addition of the sandstone resembling grey- 

 wacke, occur in the same relative position, as on 

 the opposite side. 



In particular beds of the north-west re-entering 

 angle, the claystone assumes a brecciated appear- 

 ance. Sandstone occurs, which appears to be a 

 mixture of claystone and quartz. The overlying 

 slaty-felspar, contains minute portions of a crys- 

 ' tallized matter, like vesuvian or garnet. In other 

 specimens, the felspar inclines to hornstone. The 

 whitish debris of the felspar and claystone, is par- 

 ticularly conspicuous, in the re-entering angle that 

 faces the north under the summit, where it covers 

 the whole of the east side, almost to the bottom 

 of the ascent. 



Along the Kirk- Burn, which runs eastward, 

 from the great north east re-entering angle, the 

 usual phenomena of this mountain are to be ob- 

 served. The felspar and claystone may be found 

 171 situ, at a lower elevation than elsewhere, and 

 in the vicinity of the conglomerate and sandstone, 

 which here form considerable heights to the north 

 of the rivulet. Among the debris of this stream, 

 I met with a beautiful specimen of the Petrosilex 

 of the Swedish mineralogists ; it is porphyritic 

 compact felspar, approachmg to hornstone, with 

 crystals of hornblende, and a fracture compound- 

 ed of the splintery and conchoidaL 



