8G 



GEOLOGY OF ARRAN. 



' 



Old Red as we ascend the burn above 

 the wood, the junction being somewhere 

 about the place where the wall enclosing 

 the new plantation abuts against the 

 bank of the stream. But the contact 

 is not seen, nor is there any gradation 

 visible. The Old Red is here a hard 

 quartzose slaty sandstone, with many 

 thin brown laminae, and elliptic blue 

 or white claygalls; the dip is back 

 against the slate of the mountain, con- 

 trary to that of the overlying carbon- 

 iferous beds, at angles varying from 55" 

 to 70. As we advance the strata become 

 much obscured by debris; and a little 

 above the point where the west-burn 

 enters the main stream the dip is 

 reversed or towards S.S.E., at about 

 G5 to 70. The rock is here coarser, 

 and contains imbedded masses of resin- 

 ous quartz and dark blue slate: farther 

 on it is darker and finer, with claygalls, 

 and the dip again appears to be towards 

 the slate, but the stratification is obscure. 

 In front of the first waterfall, amid a 

 group of birch trees, a mass of quartz- 

 iferous hornstone porphyry lies across 

 the bed of the stream, but seems to 

 terminate against the bank on the west 

 side ; on the east side its extension cannot 

 be traced, so that most probably it is 

 not a dike. It is a beautiful rock, and 

 if readily obtained in quantity might be 

 used for ornamental purposes. The base 

 is a dark reddish hornstone, containing 

 crystals of glassy felspar, and round 



