ii4 



MINERALOGICAL QUERIES. 



10. Does the Craig of Ailsa in the Frith of 

 Clyde, belong to the newest floetz-trap for- 

 mation ? 



Several years ago, I made a hasty examination 

 of that rock, and then it appeared to me, in con- 

 formity to the then prevailing ideas regarding 

 sienite, to belong to the sienite -formation. Since 

 that period, I have found, that certain rocks for- 

 merly considered as sienite, are but sienitic-green- 

 stone, and that this greenstone occurs in primitive 

 and floetz countries ; and that these greenstones 

 are distinguished from each other, not only by 

 geognostic, but also by oryctognostic relations. A 

 consideration of the oryctognostic characters of 

 the rock of Ailsa seems to point it out as floetz 

 sienitic-greenstone, and one that probably belongs 

 to the newest floetz-trap. 



11. Does pitchstone occur in beds in the pre- 

 vailing sandstone formation in the island 

 of Arran ? 



A peculiar variety or sub-species of pitchstone 

 of a green colour, occurs very abundantly in the 

 island of Arran, in the form of veins that traverse 

 granite, sandstone, &c. These veins are some- 

 times parallel with the direction of the strata, 

 and mi ght be confounded with true beds : in other 

 parts of the same highly interesting island, great 

 bodies of pitchstone are to be observed, running 

 parallel with the htrata ? in the form of Jbeds ? for 



