118 



MOUNTAIN OR CARBONIFEROUS LIMESTONE. 



which in traversing from the south side of the hill to the coal, cuts through a great thickness of 

 the underlying grits and conglomerates. From this work and several natural sections on the slopes 

 of the hills between the Cornbrook coal-field, and the carboniferous limestone, there can be little 

 doubt that this member of the series has a thickness of several hundred feet. The millstone grit is 

 inclined at high angles near its exterior margin, the inclination decreasing as it passes beneath the 

 coal seams. The grits, which are coarse pebbly conglomerates in the ridges above the limestone 

 at Knowl, thin out in their prolongation to the Knowlbury field and pass into sandstone. 



Mountain or Carboniferous Limestone of the Titterstone Clee Hills. 



This limestone could never have been deposited in a continuous zone, since it appears 

 only in two small masses near the northern and southern extremities of the tract, where 

 it is separated from the productive coal-field by the millstone grit, and thins out between 

 that formation and the Old Red Sandstone. (See Map and Section, PI. 30. fig. 6.) Let 

 us first consider the southern mass which lies between Cornbrook and Knowl. 



This limestone extends in a broken and tortuousb and from the gorge below the Cornbrook level 

 to Bennett's End near Knowlbury, forming a natural escarpment, which rises to some height above 

 the adjacent country of Old Red Sandstone. It terminates at the eastern end in a mural mass 

 nearly vertical, from 15 to 18 paces in width; and at the western extremity near Bennett's End 

 tapers away to a few feet in thickness, dipping beneath the millstone grit and coal measures 60° 

 north-east 1 . In the central part of this zone, the strata are much thicker and less inclined, dipping 

 to the north or to points east and west of that direction, according to the flexures or breaks of the 

 promontories. (See Map, also Section PI. 30. fig. 6.) 



At the Stable and Navers quarries the limestone is exposed in fine precipitous escarpments and 

 is largely worked. The following may be taken as a section of the whole of the calcareous strata, 

 although there is no one natural section, in which all these beds can be seen in the same quarry. 



Feet. 



Upper limestone in thin courses with shale 40 



Cropstone 5 



Great limestone or White stone 54 



Limestone shale, &c 36 



Furnace stone, a strong hard stratum of impure limestone, which from the sand 



and clay it contains is apt to vitrify in the kiln 6 



Lower limestone shale with thin bands of impure limestone 60 



Maximum thickness in all about 200 feet. 



Although this may be taken as a sample of the whole of the limestone when fully developed, the 

 appearances in different parts of the escarpment are exceedingly variable. The west end of the 

 quarries at Gorstley Rough, presents merely a thin course of limestone and shale, which expands 

 rapidly to a thick bed of fine-grained oolite resting upon coarser shelly oolite, passing down into a 



1 An adit of Mr. Lewis driven into his coal works from the low country to the west of Bennett's End has 

 proved that there was only a band of conglomerate rock of the thickness of forty-eight feet between the lowest 

 coal measures of Knowlbury and the Old Red Sandstone, the strata being nearly vertical; thus proving that the 

 limestone had completely thinned out. 



