1 865.] Hull on the History of the British Coal Measures. 21 



present bed of the Irish Sea, extending into Ireland and the Atlantic. 

 The unconformable position in which the beds of Old Red Sandstone 

 rest on the Silurian formations in these parts, conclusively proves the 

 date of these great movements. In South Wales, however, the Car- 

 boniferous beds succeed the Devonian in a nearly regular sequence, 

 and there does not appear to have been the same amount of disturb- 

 ance and denudation as in the north. The result is, that in the north 

 of England and Wales the floor of the Carboniferous beds is formed 

 for the most part of Cambro-Silurian rocks ; in the south, of Devonian. 



If we extend our inquiries into the central and eastern counties of 

 England, we pass into a region where actual observation has, for the 

 most part, to give place to deduction. The points where the Pre- Car- 

 boniferous rocks are brought into view are few and far between, but 

 by observing the changes which the coal-measures undergo on ap- 

 proaching these landmarks (as we may be allowed to call them), and 

 endeavouring to find the connection of these points with each other, we 

 have, I think, sufficient data for reasonable conclusions on the subject. 

 Now whenever these Pre-Carboniferous rocks show themselves, whether 

 rising from beneath the coal-measures, the Triassic, or later forma- 

 tions, they are found to belong either to the Cambrian or Silurian 

 systems, never to the Devonian ; we may therefore conclude that the 

 floor of the Carboniferous rocks over this area is, for the most part, 

 if not altogether, composed of Cambro-Silurian beds. 



Having thus determined the nature of the floor over which the 

 Carboniferous strata were deposited, let us now endeavour to trace 

 the original margin of the coal-formation as indicated by the uprising 

 of the older rocks at various points. 



The most conspicuous uprising of these beds in the heart of 

 England is in Charnwood Forest, Leicestershire. The Cambrian 

 rocks are here brought up on the east of the coal-field by a fault, but 

 this only hastens their natural appearance, as forming the original 

 margin of the coal-nieasures in that direction. There are several 

 other spots farther to the east where bosses of trap, apparently of the 

 age of the Charnwood Forest rocks, reach the surface through the red 

 marls of the Trias, indicating the total absence of the coal-measures. 

 From these points, if we trace the boundaries of the coal-fields of the 

 Midland Counties through Warwickshire, South Staffordshire, Wor- 

 cestershire, and Shropshire into North Wales, we shall find frequent 

 evidences of the proximity or actual appearance of a ridge or barrier 

 of land which, 1 believe, formed the margin of the Carboniferous area 

 across the centre of England. Space will not admit of detailed refer- 

 ence to each of the spots where the old rocks reach the surface. They 

 occur near Atherstone, west of Birmingham, and at the Licky Ridge 

 north of Bromsgrove. In these spots the rocks are of Cambro-Silurian 

 age. In Shropshire, however, as at Bridgenorth, the Devonian forma- 

 tion appears, having originally formed in some places the margin of the 

 Carboniferous area. The Silurian rocks, however, predominate, and 

 furnish the margin at Wellington, Shrewsbury, and along the banks of 

 the Severn into North Wales. The spots here indicated do not lie 



