416 ARRAN. PITCHSTONE. 



prove that pitchstone, like basalt, has once been in a 

 state of tenacious fluidity. 



I observed another interesting: circumstance in this 



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vein; namely, imbedded nodules or fragments of the 

 adjoining red sandstone; these being found in a part 

 which is far distant from the including walls of that 



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rock. This is the only instance, as far as I know, in 

 which fragments of the including rock have been found 

 in pitchstone veins, although an appearance not un- 

 common in trap; and it presents an interesting analogy 

 between these two substances, in addition to those which 

 are already well known. 



Another vein of pitchstone of a dark green colour, 

 is found between Garbin and Kilbride; and this rock 

 occurs in loose masses, possibly portions of veins, at 

 the head of Glen Scordel. A vein of the green variety 

 is also to be seen in Came na Caillich ; the only instance 

 in the island in which it has yet been found in the 

 granite; since, like trap, it seems chiefly to affect the 

 secondary strata. There is however little reason to 

 doubt that other veins exist in a similar situation; as 

 I procured a specimen of a black porphyritic variety on 

 Ben huish ; and since, as will presently be seen, a very 

 beautiful porphyritic variety occurs also in considerable 

 abundance in Glen lorsa. The various loose masses found 

 in different parts of the island, are oftener green than black, 

 and perhaps much oftener porphyritic than simple. Some 

 of the black varieties approach very nearly to fine grained 

 basalt. Of the porphyritic kinds, some detached masses are 

 found in Glen lorsa, not much unlike the well known rock of 

 Egg ; but of an aspect still more beautiful, and containing 

 glassy felspar in a conspicuous proportion. Similar frag- 

 ments are found on the beach below Screeb ; but in 

 neither case has any attempt to trace the origin of these 

 loose masses been attended with success. As the sand- 

 stone does not occur in that part of Glen lorsa where this 



