NOETHCMBEELAND AND DUKHAM. 5 



II. UPPER OLD RED SANDSTONE. 



Eed Sandstone conglomerates, of considerable thickness, but 

 occupying an inconsiderable area, appear on the flanks of the 

 Cheviots at Eoddam and Biddlestone, in Northumberland, at 

 elevations from 500 to 700 feet above the sea level. In the 

 deep, narrow dene of Roddam, they are exposed for upwards of a 

 mile, consisting principally of conglomerates formed of rounded 

 pebbles of Cheviot porphyry, from the size of a pea to that of 

 the human head, scattered through a flesh and brick-red clay 

 and sand, loosely bound together by peroxide of iron. Inter- 

 stratified with these are thiu beds of harder conglomerate with 

 smaller pebbles, and thin beds of greenish chloritic, calciferous 

 sandstones, some of which contain as much as forty per cent, of 

 carbonate of lime. Above the loose conglomerates are soft thin 

 bedded red sandstones, and below them are hard red sandstones, 

 with large ripple marks. These beds are not less than 500 feet 

 thick. Organic remains I have not found in them ; but as their 

 mineral characters and geological position correspond with the 

 Old Red conglomerates of Berwickshire and Roxburghshire, they 

 may, without much doubt, be grouped with this formation. In 

 Biddlestone Burn they are close upon the porphyry of the Che- 

 viots, and they are overlaid conformably by Tuedian strata. 



The red conglomerates of the border counties are more con- 

 nected with the Carboniferous, than with the Devonian system. 

 In some parts of Scotland there is a physical break between 

 them and the Lower Old Red Sandstone. Their relations are 

 best seen in the section from Siccar Point to the northern extre- 

 mity of Berwickshire, where they distinctly rest on the upturned 

 edges of the Greywacke or Cambro-Silurian strata, and are con- 

 formably overlaid by beds of the Tuedian age, the line between 

 the two being marked by the occurrence of Soloptychius nohilu- 

 simus in the red conglomerate, and of Stigmaria ficoides in the 

 Tuedian beds. In this Upper Old Red Sandstone one determin- 

 able plant, Adianthoides Silernicus, has been found in Berwick- 

 shire ; and from similar beds in Roxburghshire I have seen casts 

 of pretty large stems, probably belonging to Sigillaria. A dry 

 fertile soil is produced by the disintegration of these rocks. 



