409 



on rocks which Mr. Murcliison proves to consist of the two upper 

 members of the Silurian system, viz. " the Ludlow rocks" and " Wen- 

 lock limestone."* As, however, these rocks rise up irregularly, like 

 separate islands, through tlie surrounding coal measures, and not in 

 their regular order of superposition, so it was obviously impracticable 

 to have determined their relative age by any local evidences ; and hence 

 no attempts could have been made to distinguish the younger from the 

 loder deposits, until the structure and organic remains of the different 

 members of the Silurian system, had been fairly worked out in other 

 districts, where these types were fully and clearly displayed in their 

 regular order. 



2. Ludloic rocks. — These rocks appear at the surface in three de- 

 tached points in this coal-field, viz. Sedgeley, Turner's Hill, and the 

 Hayes. At Sedgeley they are thrown up in an elongated ellipse, very 

 much resembling a large inverted ship, of which Sedgeley Beacon, 

 630 feet above the sea, may be considered as the keel. The upper 

 Ludlow rock, though not thick, is plainly marked by containing the 

 Leptcena lata, the Serpula gigantea, &c., and by overlying a limestone 

 v\?hich is in every respect identical with that o^ Ayviestreij or the middle 

 member of the Ludlow rocks, presenting the same lithological struc- 

 ture, i. e. a dull argillaceous grey limestone, which among other welU 

 known shells, such as the Terebratula Wilsoni and the Lingula, con- 

 tains also the beautiful Pentamerus Knightii so entirely peculiar to this 

 stratum. As at Ludlow and Aymestrey, this limestone of Sedgeley, 

 known here as the " black limestone/' forms an excellent cement 

 under water. 



Turner's Hill, a small elevation between Gornals and Himley, is 

 composed of Ludlow rocks; and the Hayes is a narrow short tongue 

 of the same, with a central band of limestone, which rises at a high 

 angle from beneath the coal measures, on the main road from Stour- 

 bridge to Hales Owen, a portion of the lower Ludlow rock being also 

 well exposed. 



2a. " Wenlock limestone." — This limestone formation is much more 

 largely developed than that of the Ludlow rocks, constituting several 

 ellipsoidal masses near the town of Dudley, which have been long 

 worked and extensively known among collectors, from the number 

 and beauty of their organic remains. Hence the rock has been usually 

 termed the " Dudley limestone." As, however, it was impossible to 

 have ascertained in this district the relative age of these rocks, their 

 different members being independently in contact with the coal mea- 

 sures, the nomenclature of the Silurian system already selected is ad- 

 hered to, because in Shropshire the Wenlock limestone, in its fullest 

 standard, rises out regularly from beneath the Ludlow rocks, and the 

 latter passing beneath the old red sandstone and carboniferous lime- 

 stone (both of which are wanting at Dudley) complete the proofs re- 

 quired. The author therefore entreats geologists not to employ the 

 term Dudley limestone except as the synonym of Wenlock, with which 



* There is one spot, however, within the author's knowledge where the 

 underground works reached a thick mass of red shale or marl beneath the 

 coal-field ; but the works having been long abandoned, no correct know- 

 ledge of these red rocks can be now obtained. 



