THE MENDIPS : A GEOLOGICAL BEVElilE. 



241 



alteration have tlioy undergone; but it would seem that 

 they largely resulted from the outpourings of volcanoes. 

 This is the earliest land of which we have cognisance. 

 Rain beat upon it ; the sun slione down upon it ; rivers ran 

 over its surface ; the waves of the sea dashed against its 

 coast-line ; giant tides swept its seaward margin. Nor was 

 it more stable than the continents of to-day. South Green- 

 land to-day is gradually being submerged ; the shores of 

 the northern Baltic are being slowly lifted out of the water. 

 The ArchiBan continent, I say, was not more stable and 

 gradually subsided beneath the waters of the great Silurian 

 ocean. On the bed of this ocean the debris torn from the 

 ancient continent by rain, by rivers, and by the waves of 

 the sea, came to rest, and were built up into the strata, 

 thousands of foot in thickness (Cambrian, Ordovician, and 

 Silurian), out of which the mountains of Wales have since 

 been fashioned and carved. From time to time islands 

 appeared in the Silurian sea, but wore submerged or washed 

 away. For long ages did this sea roll over the site of our 

 English homesteads. And then elevation of the sea-bottom 

 took place. Scotland became part of the great north- 

 western continent, and bore upon its bosom tlio broad lakes 

 of which I have spoken ; and the waters of the ocean were 

 forced to retreat southwards, till of all England only Devon 

 and Cornwall remained submerged, though an arm or inlet 

 passed upwards into South Wales and occupied the area of 

 the Mendipa. In that arm of the southern Devonian sea 

 was the Old Rod Sandstone, which constitutes the heart of 

 Mondip, formed. 



Geology, which in one of its aspects is the physical 

 geography of the past, is the history of continued change ; 

 and the Mendip area was destined soon to bo more deeply 

 submerged beneath a clearer sea teeming with ancient forms 



