in the Neighbourhood of Bristol. 199 



9. Limestone in thin strata, impregnated with ochre so as 

 to be unfit for burning. 



10. Ferruginous marl, containing a great many madrepores 

 and shells quite detached from the rock. 



11. The first quarry of limestone. 



12. The second quarry of limestone. In the limestone of 

 these two quarries the strata although separated by no inter- 

 vening substance are very perceptible, preserving an uniform 

 direction. 



13. Several thin beds of limestone which are not worked. 



14. At the distance of three or four hundred yards from 

 No. 12, the assemblage of strata begins, which forms what is 

 called the Black rock, so called from the dark colour of the 

 stone. A third quarry is worked here. This rock is 

 less tinged with ochreous infiltrations than the rest usually 

 are : it contains a great many shells and entrochi, and in its 

 cavities are found dog's-tooth spar, cubes of purple fluor, 

 acicular crystals of sulphate of strontian, and of oxide of iron. 

 Similar cavities occur in the rock of the preceding quarry. 



15. Many thin beds of limestone divided by clay, some 

 being very full of shells and entrochi, and others having 

 scarcely any traces of organic matter. Some of these strata 

 from the number of shells they contain may be recognised 

 again on the rising ground at the foot of Leigh Down near 

 the village of Leigh, on the southern side of the Avon. 



both round and oval. There has likewise been found in it a complete specimen of th« 

 head of an encrinus, and other heads of the encrinus have been observed imbedded in the 

 limestone, and but little distorted. They were first noticed by Mr. Miller surrounding 

 calcareous concretions in the black rock, which are penetrated with petroleum. 



Petroleum sometimes exude6 from the rock in small quantity ; it is very hot to the taste, 

 and is used by the masons for an external application, assisted by friction, to remove rheu- 

 matic pains. The black rock is quarried for paving stones. 



2 c 2 



