GEOLOGY OF THE BRISTOL COlL-FlELD. 



269 



differ somewhat in their lithological character. They there 

 attain a thickness of 6,000 feet, a large proportion of which are 

 Cornstones and shales. 



On looking at the geological map of our President, the Devonian 

 is only met with in isolated patches, where the beds are upheaved 

 towards the earth's surface, and afterwards denuded by the 

 action of the water. The Bristol beds are probably an equivalent 

 of the Scottish series, as seen in Perthshire and Forfarshire. 



The first notice we have of the Old Eed is seen resting on the 

 Llandovery beds to the north of Tortworth. Prom thence it dips 



Fig. 9. — Section near Tortworth. 



a Upper Llandovery.— 5 Wenlock and Ludlow, —c Devonian.— <? Trias. 



to the south towards the centre of the Gloucestershire Coal basin. 

 On the east, as at Wickham, it does not come^ to the surface, 

 because it is covered up by the Inferior Oolite and Lias. On the 

 west a much larger area of Devonian is seen, reaching to 

 Thombury. We then lose sight of it till we reach TVestbury 

 and Shirehampton, where an extensive anticlinal ridge is thrown 

 up, which reaches to Portbury. 



Fig 10 — Westlurij Anticlinal, 



Westbniy. Horfield 



Henbniy. / gtoke. 



langotgfieli 



b a c e 



a Carboniferous.— d Devonian.— ^ Lower Coal Measures.— t^ Pennant. — 

 e Fault.— /Trias.— ^ Lias. 



