117 
eolation of water, by the impervious nature of the Silurian shale which separates 
the coal measures from the limestone, and by the shafts being sunk in the fault 
itself, which, like other lines of fissure, is filled up with clay and other materials, 
so closely compacted as to form complete dams to water. At the north-western 
edge of the subterranean excavation, the fault was stripped, and the materials of 
which it is composed having thinned out, the limestone was found in contact 
with a bed of coal, the edges of which appeared bent , both the coal and the lime¬ 
stone having a slickensides polish. By boring through the limestone, a second 
calcareous stratum was found, thus completing the proofs of identity between this 
underground mass and that which rises to the surface in the hills of Dudley Castle 
and the Wren’s Nest. 
In the northern or Wolverhampton field, where the whole of the coal mea¬ 
sures, even to beneath the lowest beds of ironstone, (the blue fiats), are traversed 
by shafts not exceeding 120 yards in depth, the field has been proved at several 
points to rest on shale and impure limestone, the equivalents of the Ludlow and 
Wenlock formations. For lists of the fossils in this group of Upper Silurian 
rocks, the author refers to previous memoirs, announcing that more perfect lists 
will shortly be laid before the public in his large work upon the Silurian system. 
3. Lickey Quartz rock, Caradoc sandstone, (Lower Silurian rocks).—• 
Dr. Buckland first called the attention of geologists to the Lickey quartz rock ;* 
and, showing that it had been one of the principal magazines of the quartz peb¬ 
bles in the new red sandstone and diluvium of the southern counties, he further 
compared it with certain rocks in situ in the neighbourhood of the Wrekin. The 
Rev. J. Yates has also clearly described the lithological structure of this rock, and 
has briefly touched upon some of its fossils.f Mr. Murchison undertakes to prove 
the true geological position of these rocks. He shows that they lie in the direct 
prolongation of the Silurian rocks of Dudley, and that, being partially flanked and 
covered by thin patches of coal, they emerge through a surrounding area of the 
lower new red sandstone and calcareous red conglomerate (described in previous 
memoirs). Unlike, however, the succession in the Dudley field, there are here 
no traces of the Ludlow rock and Aymestrey limestone. Nor are there masses of 
any size of the Wenlock limestone ; but shreds only of the shale or lower part of 
this formation, with some of its well-recognised fossils ( Colmers). 
The lower Silurian rocks rise from beneath the Wenlock shale in thin courses 
of bastard limestone, alternating with red and green courses of sandstone and 
shale, the equivalents of those bands which, at various places in Shropshire and at 
Woolhope in Herefordshire, constitute the top of the formation of Caradoc sand- 
® Transactions Geol. Soc., 1st Series, vol. v., p. 507. 
Transactions Geol. Soc., 2nd Series, vol. ii., p. 137* 
