South-western Coal District of England. 295 



scarred with deep^ conical, and often very extensive hollows^ wliich probably 

 are ancient ochre-pits ; the largest are those on the east of the Harptree 

 road ; to the west of the road, the sand beneath the chert is still worked for 

 ochre. The southern border of the platform, near the Castle of Comfort, 

 reposes immediately on mountain limestone ; but with this exception through- 

 out the whole escarpment of the platform, horizontal strata of dolomitic con- 

 glomerate, of the ordinary character and appearance, may be traced beneath 

 the ochreous sand and chert. 



The two hills on either side of the Tar Hall valley, which, except at their 

 very summits, consist of old red sandstone, are crowned with blocks of the 

 cherty sandstone, very compact, including fragments of the old red sandstone, 

 and abundantly charged with heavy-spar. On the summit opposite to Egar- 

 hill on the south, we find many conical pits, which were probably sunk in 

 order to obtain calamine from the conglomerate beneath the chert. 



We shall now proceed to trace the extent of the conglomerate, and to de- 

 scribe some of its more remarkable local appearances in the district. 



It skirts the whole southern side of the Mendip chain from Shepton Mallet 

 to the Bristol Channel, spreading itself out to the breadth of more than a mile 

 in the neighbourhood of Wells, but forming a narrow band towards the west, 

 where bordered by the marshes of the Axe ; it appears also in some insulated 

 hills which project above the surface of these marshes. Some handsome 

 pillars in Wells cathedral, having the character of a brecciated marble, have 

 been quarried from this rock. In the neighbourhood of Wells, and at Bleydon 

 near the Bristol Channel, it forms a beautiful breccia, called wonder-stone, 

 consisting of yellow transparent crystals of carbonate of lime, disseminated 

 equably through a dark-red earthy dolomite. Tlie cavern of Wokey hole, and 

 the chasm flanked by mural precipices by which it is approached from below, 

 are excavated in the conglomerate. It attains in the neighbourhood of 

 Wokey a considerable elevation along the hangings of the limestone chain ; 

 and in the frequent insulated masses of it, which remain scattered along the 

 slopes of the chain between Wokey and Cross, it has left traces of its former 

 extent at the same high level. On the high table-land in the centre of the 

 Mendip chain, and at the opposite extremities of the old red sandstone ridge 

 north of Priddy, are two extensive insulated masses of the conglomerate, which 

 probably occupy hollows in the lower limestone-shale. The eastern of these 

 masses is at Chewton minery, and comprehends also the Priddy mineries ; the 

 western is at Highdon farm. Considerable mines of lead and calamine were 

 formerly worked in and near the former of these masses ; the calamine was 

 worked in conglomerate ; the lead principally in mountain limestone. 



VOL. VI. 2 Q 



