Geology of Coalbrook Dale. 



425 



old red sandstone or Silurian rocks; but as we proceed north, the carbonife- 

 rous hmestone is g-radually developed. Between Harris's Coppice and Little 

 Wenlockj a very thin bed of limestone crops out from below the coal-measures, 

 and abuts, to the north, against the trap of Little Wenlock. The limestone* 

 again appears, in increased importance, to the north-west of Little Wenlock, 

 constituting a singularly displaced band in the midst of the coal-measures, 

 and extending northward about one mile, in which direction it passes, with a 

 slight dip, conformably under the coal strata, whilst to the east and west it 

 abuts against them. (Map, PI. XXXV.) The true outcrop of the hmestone 

 ranges from the south-west of the trap of Little Wenlock by the Oldfield 

 works, reposing upon the Caradoc sandstone and trapf, and thence trends 

 N.N.E. to the Hatch and Steeraways, cropping out from under the coal- 

 measure, and rising against the ridge of trap, at an angle of 40° at the Hatch, 

 and of 25° at Steeraways. At the latter place its thickness is considerably 

 increased, as is proved by the following section : 



Yds. Ft. In. 



1. White clod Shale 3 01 Coal Measure* 



2, A hard gritty rock. Pebbly sandstone 10 OJ 13 yds. 



Urchins Clay and impure limestone 



Blacks Dark bituminous shale 1 



Clod Shale 



Fiery grit Hard coarse sandstone 



Welsli Jack Very hard compact fine gray sandstone 



Gallys Shaly limestone 



Thick Measure . . Dark gray argillaceous limestone 



Binds Dark argillaceous fissile sandstone .... 



1 

 

 1 

 

 



1 



Ragged measure . . Lighter coloured limestone 



Clod and binds . . Shaly sandstone 1 



Brown measure . . Limestone 



Binds Fissile sandstone 



Double measure . . Limestone 



Binds Same as (14) 



Rough measure . . Limestone 1 



Tough measure . . Ditto, harder 



Flags Hard sandstone 



Beadstone Very impure clayey limestone 1 



Blacks Bituminous shale 



Hard white rock. .Hard sandstone, a few feet below which the 



basaltic rocks appear 1 



2 

 

 

 1 

 2 

 2 

 2 

 1 







9 

 2 9 



1 6 



2 9 

 

 6 



6 



1 6 

 1 6 



1 



Carboniferous 

 Limestone. 



^Average speci- 

 fic gravity of 

 the limestone 



2-67. 



16 1 S 



* The fossils in this rock agree with those of the adjacent limestone of Steeraways, which Mr. 

 Murchison has shown, by its organic remains, to belong to the carboniferous series. 



f 1 am rather inclined to think that a deposit of trap of variable thickness underlies the car- 

 boniferous limestone from its first appearance near Little Wenlock to Steeraways. 



