ROCKS OF SHROPSHIRE. 647 
believe that the ridge is cut across by a fault. This view is sup- 
ported by the abrupt change in lithological characters. At the 
point of junction the ridge is cut into by a ravine on the N.W. 
slope. The felstone spur forms one side (S.W.) of the hollow, and 
on its N.E. curve the red rock breaks up through the soil. 
The red rock is granitoid in character and probably of clastic 
origin. (See Note B, p. 664.) Its rectilinear junction with the 
grey rock seems to negative the supposition of an amorphous mass. 
The grey band is uncrystalline, much jointed, and very variable 
in colour and hardness. To the naked eye, it looks very much like 
a tuff, containing fragments of the characteristic Wrekin rhyolite, 
some of which are distinctly banded. Some of the included bits are 
rounded, like pebbles. Prof. Bonney is, however, clearly of opinion 
that this singular rock is simply another form of the Wrekin rhyo- 
lite intrusive in the red rock. (Note A, p. 663.) This revelation 
by the microscope is very interesting and important, and will be 
a great aid in correlation. 
Along the 8.H. flank of the hill strike the thick beds of quartzite, 
succeeded by the Hollybush Sandstone and the Shineton Shales, 
described in previous papers*. The quartzite probably holds the 
same position on the N.W. of the axis, but exposures are very 
scanty. 
Summary.—A 8.W. ridge composed of a bedded granitoid rock 
dipping southerly, and underlain by eruptive Wrekin rhyolite, at the 
N.E. end, and of grey and brown felstones with a N. dip for the 
remainder of its length, the two series being separated by a fault, 
the ridge being flanked by quartzite on the N.W., and by quartzite, 
followed by Cambrian strata, on the 8.E. 
3. Lawrence Mill (figs. 2, 4, 5). 
Details—The north-east end is composed of felstones similar to 
the opposite crags of the Ercal, and felstone may be traced all along 
the crest of the hill till we reach the edge of the great quarry, which 
exposes a considerable part of a transverse section of the chain. It 
was this magnificent exposure which first convinced me of the 
erroneous interpretation of the Survey. This supposed eruptive 
greenstone consists of felspathic tuff+, clearly bedded, and dipping 
north at 50°. The true bedding is much obscured by jointing, but 
it may be made out most satisfactorily by following beds to the 
right or left. Continuity of texture is thus as clear a proof of 
stratification as continuity of mineral composition in ordinary 
sedimentary rocks. The bands vary from a fine-grained ash to 
a breccia or a conglomerate. Even hand specimens sometimes 
distinctly show alternations of fine and coarse bands. In addition 
to this evidence of stratification, the seams separating beds and the 
exposed surfaces of the beds themselves are clearly visible. The 
coarser bands contain fragments of pitchstone and of felstone, the 
* Quart. Journ. Geol. Soe. vol. xxxiii. p. 652, and vol. xxxiv. p. 754. 
+ Described by Mr. 8. Allport, Quart. Journ, Geol. Soc. vol. xxxiii. p, 458. 
