James Neihon — Old Red and Carboniferous of Arran. 225 



sequence has been recorded or observed, I am inclined to relegate 

 them to that position. These sandstones, etc., were descrihed by 

 Sedgwick, Mnrchison, and Ramsay, as belonging to the New Red 

 Sandstone formation, while Bryce sets them down as belonging 

 to the Upper Carboniferous series (we presume the equivalents of the 

 Bothwell red sandstones, which overlie the highest of the Lanark- 

 shire coal-seams). 



In Sir Archibald Geikie's Geological Map of Scotland, published 

 1892, these rocks are set down as Upper Old Red Sandstone ; but 

 they clearly overlie, probably, one thousand fathoms .of strata con- 

 taining Carboniferous fossils; and, more astonishing still, the pebbles 

 of the breccias in these red sandstones contain fossils of Carboniferous 

 age, originally discovered by Mr. James Thomson, F.G.S., a fact 

 well known to the members of this Society many years ago. 



These rocks, then, may be considered as the highest rocks in this 

 part of Arran, and it is evident that the Upper Coal-measures are 

 absent. 



I have already stated that the ring of slates or schists completely 

 encircles the granite, but Sir A. Geikie's map shows, on the east, 

 the granite in contact with the Old Red Sandstone for a 

 distance of about three miles. This is not so in the White 

 Water (described in all the Handbooks), nor in the Punch Bowl, 

 or Coich-na-Oich junction, where the gi-anite and slate can be seen in 

 contact. The rocks here are coloured as Lower Old Red Sandstone, 

 while I am inclined to regard them as Upper Old Red Sandstone. 



For comparison with the Arran rocks I append Sir Archibald 

 Geikie's Synopsis of the Carboniferous Limestone Series of Scotland. 1 



w § Group of sandstones and shales, with three or more seams of limestone 



(Castlecary, Calmy or Ardeu, and Index limestones). 

 =2 ffi J Sandstones, shales, coals, and ironstones, but with no limestone band*. 

 § § J Sandstones, shales, fireclays, corals, and ironstones, with several thin lime- 

 £ <S I stones (Hosie's) towards the top, and the thick main or Hurlet Limestone 



-2 at the bottom. 



^ { 



This, it will be seen, agrees with the Arran section. 



And now, in conclusion, I cannot help asking the question — Is 

 there any way of accounting for the redness of the Arran rocks, so 

 different in many cases from their equivalents elsewhere ? 



The ironstones appear to have been deposited in a manner exactly 

 similar to the Clay-bands of the mainland, and I am strongly of 

 opinion that originally they were similar, and that the alteration to 

 peroxide took place subsequently to their deposition and segrega- 

 tion, and was due to some change which did not apply to the West 

 of Scotland generally. 



I am inclined to attribute this change to heat, The red rocks of 

 Arran are situated round, and at no great distance from, a granite 

 nucleus, upheaved to its present position subsequent to the deposition 

 of the stratified rocks, and it is just possible that to the long-continued 



1 Explanatory Notes accompanying a new Geological Map of Scotland. 1892. 



DECADE IV. — VOL. IV. NO. V. 15 



