no 



MINERALOGICAL QUERIES. 



sition -rocks or the newest floetz-trap forma- 

 tion* ? 



Some time ago, I visited Fassney-burn, with the 

 view of ascertaining whether or not this rock was 

 granite, as asserted by Professor Playfair 4% The 

 rock appeared to me, to resemble certain varieties 

 of sienitic greenstone ; but I could not afford 

 time to determine its geognostic relation to the 

 transition-rocks which form the great proportion 

 of that part of the county. 



* Since this query was proposed, Dr Ogilby of Dub- 

 lin has examined the country around Fassney, and is of 

 opinion, that the rock is greenstone, and belongs to the 

 transition class. 



f " Another instance of real granite disposed in regu— 

 " lar beds, but without any character of gneiss, is one 

 •* which I saw in Berwickshire, in Lammer-muir, near 

 " the village of Priestiaw. The little river Fassnet, cuts 

 f* the beds across, and renders it easy to observe their 

 " structure. The beds are not very thick ; they run 

 " from about S. S. W. to N. N. E. like the schistus- 

 " on either side of them. I was in company with Sir 

 " James Hall when I saw these rocks. We examined 

 " them with a good deal of attention, and traced them 

 44 for more than a mile in the bed of the river ; and, if I 

 tf mistake not, our opinions concerning them were pre- 

 •* cisely the same." 



Playfair's " Illustrations," p. 328. 



