74 REPORT—1857. Pa 
He exhibited a sketch section through each of these localities, which gave as a 
result the following facts:— 
Ist. Near Llandeilo the Upper Silurian beds are capped by a narrow band of very 
micaceous yellowish flags and grits, occasionally conglomeritic, and frequently fossili- 
ferous. Below these are dull red and purple beds, alternating with grey slates and 
grits near Llangaddock, of which the following section is given by Sir H. De Ja Beche 
(Memoirs of Geological Survey, vol. i. p. 28) :-— 
Red sandstones, hard and soft . . . s »« =» « + + 600 
Purple and red conglomerate and sandstone .-. . . . 66 
Ditto, with micaceous bands, fossiliferous . . , . . . 40 
Purplish grey thin micaceous sandstone . . . . . . 40 
Dittos fess liferouss) Gv ae sr etesneclters Mee we eel eee 
hine:efifedcunglomeyate fy. it ier x ind ye. bike, see 
1075 
Below are about 2000 feet of Upper Silurian rocks of the ordinary blue and grey 
colours. 
Above this band of micaceous flags, here and elsewhere, for a distance of many 
miles, blood-red marls and shales set in, alternating with red sandstones, and fre- 
quently containing beds of the red or greenish or mottled calcareous sandstones, 
or concretionary limestones known as Cornstones. These beds are frequently and 
excellently shown over a band of country a mile wide and twelve miles long, from 
Middleton Hall to the Sawdde, near Llangaddock, and always vertical, or nearly so. 
Between them and the escarpment of the carboniferous limestone, to the south is a 
narrow richly-wooded valley in which little or nothing could be seen, except near 
Castell Cwm Cennen, where a mass of carboniferous limestone is brought down by 
a fault close against some of these vertical beds dipping at them at 20°, the Old Red 
Sandstone between this detached lump and the escarpment of carboniferous limestone 
being gently arched and contorted, and then dipping conformably under the carboni- 
ferous rocks, which it was seen to do everywhere in the neighbourhood. 
Six miles east of Llangaddock, in the glen of Llechclawdd, these same rocks with 
strong cornstone bands dip 8.E. at 70°; but on proceeding into the red district, the 
angle soon flattens to 45° and 20°, but without any appearance of want of conformity, 
while further on, five miles east by south of Llandovery, Silurian rocks and Old Red 
Sandstone alike lower their angles of dip to 30° or 40°; and as we proceed towards 
Brecknock, the Old Red Sandstone beds containing the Cornstones undulate in various 
directions, at angles never exceeding 5° or 10°. ’ 
What may be the exact nature of the overlap towards the west of the red rocks 
over the Upper Silurian, and of the upper part of the red rocks over the lower part of 
the same, and finally of the carboniferous rocks over the Old Red till the coal-measure 
rest directly on the Lower Silurian, he had no time to inquire. 
2ndly. A walk across the Beacons of Brecon showed that from the Cornstones deep 
down in the Old Red Sandstone to the base of the carboniferous limestone, there was 
no apparent break. Red marls occurred throughout, containing brown and grey 
flagstones and sandstones with no conglomerate worthy of the name, all dipping 
south at about 5°. 
3rdly. On examining the narrow valley of the Usk, however, near Pontypool, the 
Upper Silurian rocks were found to differ greatly from those near Llandeilo and Llan- 
dovety. There were no red beds in them, no appearance of any graduation between 
them and the Old Red Sandstone, and finally they either plunged at high angles with — 
some contortion and obliquity towards the valley of Old Red, or as at one place dipped 
directly from it at 25° close to the boundary, while the Old Red Sandstone inclined 
towards the carboniferous escarpment, at angles varying from 10° to 30°. Here then 
there appeared to be a possibility, at all events, of an unconformity between the Old 
Red Sandstone and the UpperSilurian, and a possible concealment therefore of the lower — 
beds of the Old Red Sandstone, which have a conformable junction with the uppermost 
beds of the Ludlow rocks, beneath the unconformable beds of the Upper Old Red, 
This conclusion, though based on very slender evidence, is strengthened by the fact 
of the section here giving, with all allowances, a thickness of only 2500 feet for the 
