I860.] GEIKIE OLD RED SANDSTONE. 323 



Scotland stretched away from south-west to north-cast as a long 

 island, indented by narrow inlets and curving bays. Some parts of 

 the coast-line were low and sandy ; but a large portion seems to have 

 resembled the existing coast at St. Abb's Head, and to have risen as 

 a perpendicular cliff-line worn into clefts and stacks, and deep ocean 

 caves. The sea probably ran in broad sounds between this island 

 and the Cumbrian mountains on the one side, and the southern flank 

 of the great Grampian chain on the other. 



From the commencement of the Upper Old Red and onwards 

 through the Carboniferous, the land underwent a process of sub- 

 sidence, which, though in its later stages often retarded and even 

 reversed, yet continued the dominant movement in this part of the 

 country. 



As it went on, the long Silurian and Lower Old Red island became 

 narrowed in outline, the bays on either side advanced nearer to each 

 other, until by degrees they met, and the main island merged into 

 an archipelago. The stages of the subsidence, in so far as they can 

 be made out in the region of Lammermuir, will shortly be described 

 in the Memoirs of the Geological Survey. "What I more especially 

 wish to point out at present is, that from the facts presented in this 

 paper we were led to notice that the west part of the island con- 

 tinued above water long after the eastern part had become submerged. 

 That area which now forms the southern portion of Lanarkshire and 

 Ayrshire, perhaps along with much of the adjacent district, continued 

 to be land when the site of the Lothians and Berwickshire had sunk 

 below the sea and become covered over with many thousand feet of 

 sedimentary matter. It was not until the whole of the Upper Old 

 Red Sandstone, and nearly the whole of the Lower Carboniferous 

 group had been deposited, that the bases of the Lesmahago Hills 

 were washed for the first time by the waves of the encroaching sea. 

 Either, therefore, the south-western district of Scotland must have 

 stood several thousand feet higher than the south-eastern, or the 

 rate of submergence must have been greatly more rapid over the 

 latter area than over the former. 



It would be premature, without many more additional details, to 

 decide which of the two suppositions is the true one, although a 

 difference in the rate of submergence seems at present best to explain 

 the facts. There are also other points connected with the ancient 

 physical geography of southern Scotland on which 1 much wish to 



touch; but 1 must delay their consideration until I am ahle to lay 

 before the Society the results of another visit to the uplands of 



Peebles and Lanark. 



