234 Proceedings of the Royal Physical Society. 



can also observe the transition from pitclistone to porphyry- 

 slate or basalt.* 



" This pitchstone, from its occurring along with porphyry- 

 slate, and lying over transition rocks, is to be referred to the 

 newest floetz-trap formation.-[- 



" Odservatio7is. 



"Werner has hitherto described but one pitchstone for- 

 mation, and it belongs to the primitive rocks. Several years 

 ago I observed, in the highly interesting island of Arran, 

 pitchstone alternating with floetz greenstone that lay over the 

 independent coal forniation.J Afterwards I saw it in veins 

 traversing floetz-trap rocks in the Isle of Eigg§, and among 

 similar rocks in the Isle of Mull.|| 



" Since that time Werner has examined the black pitch- 

 stone of Zwickau in Upper Saxony, which he considers to 

 belong to a similar formation. Mr Humboldt, the celebrated 

 and enterprising Prussian traveller, whilst on the summit of 

 the Pic of Teneriffe, observed beds of pitchstone among floetz- 

 trap rocks ; and I have seen in the interesting collection of 

 Captain-General von Charpentier specimens of a similar fossil 

 that was found in the basaltic country of the Veronese. We 

 have thus proofs that this pitchstone is subordinate to the 

 floetz-trap formation, and that it is widely distributed." IF 



Three years after the appearance of the volume from which 

 these extracts are taken, Jameson gathered his followers 



* "This pitclistone like that of Glencloy, in the island of Arran, will pro- 

 bably be found to contain bituminous or carbonaceous matter. The pitch- 

 stone of Glencloy, when powdered, emits a bituminous smell, and colours the 

 sulphuric acid slightly ('Mineralogy of the Scottish Isles,' vol. i., p. 48). 

 Basalts and other rocks belonging to the same formation contain, according 

 to Klaproth and Lampadius, bituminous or carbonaceous matter ; and Mr 

 Pepys has discovered carbonaceous matter in wood opal and wood stone, — 

 Parkinson on Petrifactions, vol. i." 



t " Dr Reuss, of Bilin, is of opinion that porphyry-slate occurs in older 

 formations than the floetz-trap ; and Captain-General von Charpentier says 

 that basalt sometimes occurs in primitive mountains. Both these observa- 

 tions, as I have shown in my book on Mineralogy, are incorrect." 



t "Mineralogy of the Scottish Isles," vol. i., p. 23. 



§ Ibid., vol. ii., p. 44. 



W'Ibid., vol. i., p. 213. 



IT Mineralogical Description of Dumfriesshire, pp. 115-117. 



