ro 



I have no doubt that the hard volcanic rocks of both the Carneddau at 

 Builth, and the Oorudon Mountain, were once hidden and covered up by masses 

 of Upper Silaiian strata, and other later beds of deposition, which have all been 

 denuded and swept away, and thus tlie harder masses beneath have been left 

 exposed like the kernel of a peach, or a nectarine, when the softer parts of the 

 fruit have been removed. In some parts of "Wales, as along the Longmynd range, 

 we find evidence tliat the Caradoc rocks and the Upper Llandeilo deposits had 

 undergone denudation before the deposition of the Upper Silurians, for the 

 Upper Llandovery beds are seen resting on the old Cambrian rocks, as well as on 

 the Caradoc and Lower Llandeilo beds. In fact the Lower Silm-ians, with their 

 interbedded igneous rocks, had undergone a series of volcanic and earthquake 

 contortions, and a great thickness of Lower Silurian strata had been removed 

 by denudation before the vast thickness of Upper Silurian strata was accumulated. 



There are few members of the "VVoolhope club who are not acquainted with 

 the distinct groups of the Upper Silurian rocks, with their bands of limestone 

 and their beautifully preserved fossils. In the region which the club have visited 

 on this occasion the Silurian rocks are covered up by a great thickness of Old 

 Red Sandstone, and by a series of carboniferous strata which once spread north of 

 this country over the great Silurian region of Northern Wales. 



All the Upper Silurian rocks are of marine origin, as is evidenced by their 

 fossils. They are of great thickness, entering in North Wales into the formation 

 of considerable hills, and, although in certain places they are much faulted by 

 earthquake movements, display but little evidence of intruded volcanic masses, 

 or the infiltration of igneous dykes through their beds. The only example I know 

 of is the protrusion of the igneous rock of Stanner, near Kington, where the 

 old lava of Stanner is seen to traverse and metamorjjhose the Lower Wenlock 

 or Woolhope limestone. 



Above the Upper Silurian rocks are deposited a great mass of red and grey 

 sandstones, shales, and cornstones, surmounted by a series of brown and reddish 

 sandstones, known as the "OM Red Sandstone" and which has a thickness of 

 several thousand feet. Above these again, in the Silurian area, there rests a thick 

 pebble bed known as the " Old Red Conglomerate" and over this there follows a 

 series of yellow and greenish sandstones which I believe to be the real base of the 

 over lying Carboniferous series. The Old Red at its base contains a few Upper 

 Silurian shells intermingled with certain forms of peculiar fish ; while the yellow 

 beds at the summit contain Pterichthys, and Holoptychius, fish which at Farlow, 

 near the Clee Hills, are found associated with a carboniferous marine shell, an 

 Orhicula. 



With regard to the evidence of volcanic or igneous agency as associated 

 with the Old Eed we have very little positive proof. The well-known lava dyke 

 or Greenstone of Bartestree, near Hereford, and one at BrockhiU, on the Teme, 

 are the only igneous rocks I know of which are seen in contact with the Old Ked 

 rocks of Wales or Siluria. Yet we cannot but observe that great earth move- 



