16S Unconformalle Limestone in Shropshire. 



them*, is very important^ and seems to offer, in part at least, a dif- 

 ferent mode of surmounting- the great diliicultics, presented Vty 

 the yellow Limestone border, to t!ie very irregularly wide Coal- 

 field of Nottingham, Derby, York and Durham, than that ven- 

 tured to be given in ISl 1, by means of my zig-zag Faidt. I must 

 still however be permitted to say, that proofs have yet in no in- 

 stances been offered, that Faults do not range in the manner re- 

 presented in my Maps, or very nearly so, however much I may 

 have miscalculated the magnitudes of their derangements, and 

 consequent effects on the visible parts of the Strata : and that 

 even in the present instance, that stretch or line of the zig-zag 

 Fault, which I had observed passing (from Thorner) in a NW 

 and SE direction, at the foot of the Limestone edge near Kid- 

 hall, on the Road from Tadcaster to Leeds, is recognized and 

 named as sucli, in the Garforth Colliery map, received from 

 Mr. Faulds ; although a far less derangement seems there as- 

 signed to it, than I had supposed. 



In hastily examining last November, the Coal-measures at 

 Crew-Green or Bausley Colliery, (2 m. WNWofAlberbury, which 

 is in Salop,) I observed them declining E, under Red Marl Grit; 

 to which succeeds a thick Limestone Rock stretching from Al- 

 Lerbury to Caerdiston, with a NE dip, the Limestone of Avhich, 

 partakes of that extraordinary conglomerate character, that i 

 have aheady mentioned, as distinguishing this district. It mu.^t 

 however, I think, be referred to the yttiow Limestone Rock, 

 imbedded in the vast Red-marl Grit, which extends thence to 

 Shrewsbury, and further ; and it would be desirable to know 

 from an analysis, by some of your chemical Readers, in ^^'hat 

 proportion Magnesia may be a component of theAlberburj Lime- 

 stone Rock ?. 



The Corn-stctie, which is frequently a conglomerate sort of 

 Limestone, on the eastern side of the Glee Hills, at Barnaby, 

 Ince, &c. is imbedded in Red Marl or its Grit, and such appears 

 now to me (on reconsidering my observations made in July 1812) 

 to belong to the unconformable yellow Limestone Rock, and its 

 imbedding Red Marl. 



The Limestone Trough in the vale of Clwyd, which I have 



* Injustice to my iil)le and respiectcd friend Thomas Wtilker, Esq. of 

 P.abtvvood, and others of the Conl-jVJasters, alluded to at buttoni of pa;^e 

 166, of my Derby. Report, vol. i. ' and P. JM. vol. xlii. p. 110, I oiijiiit to 

 repeat here, the opinion enleitained by then;, that the Bilborough Coals 

 emerged from under and left the edge of the yellow Lime, appeariiii;, when 

 Old beyond its edge to Lie uuconfuniutble tliereuith. But none of these Gen- 

 tlemen or others mentioned, or even I believe hinted at, an unconformab't- 

 jiess, yirorw/ between Jie Coals and superincumbent Limestone, in any of 

 Cheir numerous pits in Nottinf^hanishire, sunk ttuongh die latter rock. 



described 



