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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 slick ensides 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 flats), 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.-]- 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 Gcol. Soc, 1st Series, vol. v., p. 507. 

 ■f Transactions Geol. Soc, 2nd Series, vol. iL, p. 137- 



