296 PROCEEDINGS OF THE GEOLOGICAL socieTy. [Apr. 95, 
its absolute structure. The strike of the Longmynds (part of the» 
Cambrian rocks of Professor Sedgwick) and of the Bishop’s Castle 
slates and traps (Llandeilo flags of Sir Roderick Murchison) is N.N.E. 
and $.8.W. To the south-west of Church Stretton the Wenlock shale 
and part of the Caradoc sandstone is thrown down on the west by 
the great fault already noticed. The Caradoc sandstone, in 4 thin 
band, rises from beneath this strip of Wenlock shale, and rests un- 
conformably on the Longmynd Cambrians in such a manner that it is 
plain the latter formed an original boundary to the sea of the period. 
The Caradoc, which is here a conglomerate, is composed of water- 
worn pebbles derived from the Longmynds. It folds round the 
southern extremity of the Longmynds across the strike, and is 
immediately afterwards overlapped by a band of limestone, which 
lies beneath the Wenlock shale. This limestone skirts along the 
Longmynds and Llandeilo flags to Church Stoke, across the strike of 
the older beds. Round other parts of the igneous series to the north 
the Caradoc sandstone appears at intervals, and always quite uncon- 
formably, on the Llandeilo flags. Twelve miles south, near Brampton 
Bryan, Caradoc sandstone is again seen in a small boss, resting un- 
conformably, on slaty shales. The well-known boss of the same sand- 
stone at Presteign with its overlying limestone is highly mdurated, 
occurring in the line of fault through which traps occasionally pro- 
trude. At Old Radnor another boss appears in the same line of dis- 
turbance, with similar overlying limestones. Here the rock has 
suffered a still greater amount of alteration, bemg in some instances 
almost fused. 
The occasional patches of Caradee that dip beneath the over- 
lapping Wenlocks around the Bishop’s Castle traps and. slates rise 
from beneath the Wenlock shales on their western outcrop, near the 
banks of the Vyrnwy, two miles west of Llanfair. The slates be- 
neath this Caradoe rise in an anticlinal, and in the roll to the west a 
trough of Wenlocks is again thrown in: on the west of this near 
Garthbibio, the Caradocs spread out for six or eight miles to within 
two miles of Mallwyd. . i 
If we now trace the western boundary of the Caradoc sandstone to 
the north, we find it turning round with the great Merioneth anticlinal 
of Professor Sedgwick. On the north-east of Dinas Mowddy it is 
several thousand feet above the Bala limestone, but in its progress 
north and west it gradually creeps over these higher beds, till at last at 
Yspytty Evan it fairly reaches the level of that limestone. This 
evinces unconformity. If we trace it south from Dinas Mowddy we find 
an irregular outline proceeding into Radnorshire, and everywhere at 
certain distances beneath are the intermittent beds of sandstone, which 
in some localities characterize the higher part of the slaty series on 
which the Caradoc rests. As the Caradoc rocks approach the region 
of the Builth beds they turn off to the east, as if the Builth series 
had formed a barrier to their further original deposition in that diree- 
tion. They never again appear-in the south, the Wenlock shales 
overlapping them and resting directly and unconformably on the 
Builth beds, and also on the rocks further to the south-west. 
ne a 
