656 C. CALLAWAY ON THE PRECAMBRIAN 
reddish felspathic rock, apparently a felstone, mottled with minute 
geodes of quartz, which is sometimes coated with viridite. The 
geodes show a tendency to lie in parallel planes, as if they had ori- 
ginally been air-bubbles in a lava-flow. To the 8.W. of the summit 
greenstone breaks out in the centre of the ridge, and keeps to the 
crest of the hill for some distance, being flanked on each side by 
grey felspathic rocks. Then the grey rock occupies the entire saddle, 
but greenstone soon reappears, and forms the axis of the range for a 
quarter of a mile, with the grey rocks, as before, on each side. An 
isolated boss of greenstone also breaks out on the S.E. slope. To- 
wards the S.W. end of the range is a very interesting series of 
bedded rocks, clearly dipping to the N.E., that is, at right angles to 
the trend of the ridge; they are undoubtedly fragmental and 
most distinctly stratified. Some of the beds are very thin. In 
some spots several varieties occur in a thickness of a yard. The 
common rocks are a coarse ashy shale, a coarse grit made of crystals 
of red felspar with grains of quartz, a similar grit with the frag- 
ments imbedded in a dark matrix (Note 4,p. 667), a felspathic breccia, 
anda compact felspathic rock with a flinty fracture. In one place I 
detected a thin band of quartzite, the only instance of the occurrence 
of that rock in the older Precambrian strata of the district. The 
Caer Caradoc range terminates with a mass of greenstone, which 
occupies the south-western slope, and by its intrusion has increased 
the dip of the overlying beds. 
On the Survey map this mountain is coloured as altered Caradoc, 
with four masses of intrusive greenstone irregularly arranged. 
The position of these intrusions, as well as the description of the 
bedded rocks, requires some modification. There are more than 
four eruptive masses, and they are generally arranged in a lincar 
manner along the crest of the ridge. 
The strikes in this range have been greatly disturbed by the 
greenstones. Wherever bedding can be made out in proximity to 
eruptive rock, the dip is away from the intrusive mass. On the 
whole it is probable that the original strike was in accordance with 
the prevailing E. & W. strike of the axial series. At the S.W. end, 
for example, where the bedding is most distinct, the dip is N.E.; but 
it is evident that if the intrusive boss which has disturbed the beds 
at that point did not exist, the dip would have been more northerly. 
Caer Caradoc, like the Wrekin, is a wedge of consolidated Pre- 
cambrian rock, thrust up through younger beds, and is consequently 
bounded by faults on all sides. In the Survey map, Wenlock strata 
are faulted down against the N.W. side of the ridge. This is quite 
correct as regards a part of the distance; but this Wenlock wedge 
has been carried by the surveyors too far tothe S.W. Towards the 
S.W. end of the hill the fault brings down against the axial rocks 
the slates of the Longmynd group, with their usual dip to the 
N.N.W. at a very high angle. On the S.E. side of the ridge the 
relations of the flanking strata are very complicated. At Little 
Caradoc the axial rocks are overlain by high-dipping quartzite, suc- 
ceeded by Hollybush Sandstone and Shineton Shales, with Caradoc 
