252 



THE MKNmrS: a aKOLOGICAL RKVERTE. 



tho Mcndip Islo stretched further, in all probability, than 

 the present extension of the range of hills. Nortliwards our 

 microlestes would have seen tho low island of Wriiigton, 

 and beyond it the long Clovodon and Clifton Islos. Probably 

 Kingswood formed a coal-measure island oast of the present 

 site of Bristol. Such may have boon tho outlook from Black- 

 down of old. 



Slowly the Mendip Island sank. Slowly tho waters of tho 

 inland sea crept up its flanks, receiving there certain long- 

 shore deposits visible to this day. But before tho hills were 

 submerged a change had come over tho waters of the sea. 

 No longer, as heretofore, salt and barren of life, they teemed 

 with marine creatures. Subsidence of land over Franco had 

 placed the waters of the inland lake in communication witli 

 the warm Jurassic sea that had long rolled over the region 

 in which the Alps were subsequently to be upheaved as a 

 magnificent mountain range. 



One of the most interesting chapters of Mendip geology is 

 that which deals with the gradual submersion of tho island 

 beneath the Triassic and Liassic sea. The earliest deposit 

 which speaks to us of this submergence is tho so-called 

 Dolomitic Conglomerate. It contains, comonted into a giant's 

 " pudding stone " of often considerable hardness, huge irregu- 

 lar fragments of the local rocks that had perhaps lain at the 

 surface during the long period of sub-aerial waste and decay, 

 I have at times been tempted to boliovo that some of the 

 linger blocks must have been ice-borne, but I have no evi- 

 dence that such was tho case. And it is j)erliaps more 

 probable that they were swept from the hills by floods. 



While this deposit was being formed along tho shore lines 

 of the ancient islands, Keuper marls were being laid down 

 at a little distance from tho margin. But whereas the 

 Keuper Deposits of Cheshire are some 3,000 feet in thickness, 



