268 



GEOLOGY OF THE BHI8T0L COAL-FIELD. 



Pig 7. — BrocTchy Combe Section. 



Beacon 

 Batch. 



Brockley 

 Combe. 



c b a b e 



a Devonian. — b Lower Limestone Shales. — e Carboniferous Limestone. 



Carboniferous, and in point of sequence intervenes and separates 

 it from the Silurian. 



In many places the junction between the Devonian and 

 Carboniferous beds is exposed; as for instance at the side of the 

 Avon, under Cook's Folly (Fig. 8). 



Fig. 8. — Junction of Devonian and Carhoniferous at- Cooh''.^ Folly. 



Carboniferous 

 Devonian 



/ 9 



a Micaceous bed?.— i Quartzose Conglomerates.— c Three beds of rolled 

 Quartz pebbles— f? Lust bed of rolled Quartz. — e First Calcareous bed. 

 — / Mhyris bed. —g Entomostraca and plants. — h Modiola bed. 



The transition from one to tho other is so gradual that the 

 cessation of the Devonian and the commencement of the Lower 

 Limestone shales can with great difficulty be determined. In 

 this district the Devonian rocks attain a thickness of about 4,000 

 feet. 



The beds that are found in the Bristol Coal Field belong to 

 what are termed the Middle Devonian. On the north side of the 

 Bristol Channel the Devonian beds arc much more developed, and 



