CHAP. VI.] CARBONIFEROUS PERIOD. 83 



Carboniferous system can be traced all round it. They 

 sweep over the high ground on the borders of Berwick and 

 Haddington, and seem to have covered the whole of the 

 Lammermuir Hills, but the central uplands of Lanark, 

 Peebles, and Selkirk may have remained above water 

 during the greater part of the period. There is, indeed, 

 no evidence that they were ever submerged. The Calci- 

 ferous sandstones are clearly shore-beds deposited on an un- 

 even and irregular surface, and it would be very unsafe to 

 assume that those at the higher levels must have been suc- 

 ceeded by the whole series of Carboniferous rocks which 

 are found to the north or south of such tracks. It is pro- 

 bable that the sandstones represent higher and higher parts 

 of the series as they near the higher ground, and that the 

 conglomerates which fringe the Carboniferous rocks were 

 formed on the slope of a sinking coast-line. There is, in- 

 deed, positive evidence in the south of Edinburgh that the 

 whole of the beds below the Limestone group have thinned 

 out, for south of Magbiebill an outlier of the limestone 

 rests directly on the Lower Old Red Sandstone. Here, 

 therefore, more than half the thickness of the Scotch Car- 

 boniferous system has died out against the slope of the 

 southern uplands, so that it becomes highly probable that 

 this hill region was above water till the close of the Lime- 

 stone epoch, and if the Millstone Grit was formed during 

 a slight upheaval, as many think, the land area would then 

 have been somewhat enlarged. 



It may be advisable to point out that the existence of the 

 great boundary fault does not invalidate the above conclu- 

 sion. If this were a post-Carboniferous dislocation it might 

 be said that the ground on the upcast side was so much 

 lower in Carboniferous time that it might have been covered 

 by the limestones ; as a fact, however, the limestones and 

 coal-measures are not broken by the fault, and in the south 

 of Edinburgh it seems to have given rise to a steep bank 



