434 J. PrestwicHj Esq., on the 



only to be judged of by hand-specimens, I could not ascertain whether any. 

 fossils existed in them. 



A gray and brownish very hard limestone, with a conchoidal fracture, and 

 varying from one to two yards in thickness, crops out atTasley near Bridge- 

 north. The lime made from it, is in general applicable to agricultural pur- 

 poses only, but in some cases it is well adapted for a water cement. At the 

 Amies it apparently consists of fragments of a gray limestone imbedded in a 

 whitish calcareous paste. This bed of limestone was first noticed by Mr. 

 Murchison in a memoir read before this Society in 1834, and shown by him 

 from its organic remains to be of freshwater origin. He has detected the 

 band, at intervals, along a devious outline extending to the edge of the Bred- 

 din Hills, but always in the same geological horizon. It is but lately, that I 

 have been enabled to ascertain its true position in the Coalbrook Dale field, 

 as it had hitherto been explored at its outcrop only, where but a few feet of 

 clay or marl overlie it. 



In September 1836, I found at the mouth of a pit*, then sinking between 

 the Amies and the Tuckiss, a considerable quantity of the same limestonef . 

 The bed was about 4 feet thick, 90 yards from the surface, and 10 yards 

 above a sulphur coal, about 125 feet above the clod coal, or only 170 feet 

 from the base of the formation ; but this part of the field being apparently of 

 littoral formation, the connexion of the strata between this locality and those 

 where marine remains occur;}; is not yet clearly ascertained, for I have been 

 unable distinctly to detect this band of limestone on the north of the Se- 

 vern. Nevertheless, by tracing the prolongation of the bed by means of a 

 few of the associated strata, its equivalent in other parts of the coal-field may 

 be approximated to. Accordingly, at New Hadley and Woombridge, the 

 place which this freshwater stratum should hold may be somewhere about 

 that occupied by the marine deposit of Chance Penneystone. 



A few of the thicker lower sandstones are extensively quarried for build- 

 ing-materials ; the principal so employed being those above the little flint 

 coal, the Penneystone, the flint coal, and ball-stone. The first makes the best 

 hearthstones for the iron furnaces. The beds of clay are numerous and va- 

 luable. The Shropshire fire-clay vies with that of Stourbridge; and its 

 bricks are sent to all parts of the kingdom. Many of the " Pounstones " form 

 good fire bricks. A peculiar difference marks two of the ironstone shales. 

 The shale in which the Penneystone is imbedded, is extremely injurious to 



* See section of Amies pit, Diagram, PI. XXXVII. 

 •j- Its specific gravity is 2'65. 



X It is to be observed that in no instance lias tlie Penneystone with its marine reliquiae been 

 found immediately underlying this freshwater limestone. 



