BEFORE AND AFTER 75 



Liassic strata stretch across England from Lyme Regis 

 in Dorset to Whitby in Yorkshire. Most of the strata 

 we are describing run across England from south-west to 

 north-east. After they were laid down a movement of 

 elevation, connected with the movement which raised 

 the Alps in Europe, took place along the lines of the 

 Welsh and Scotch mountains and the chain of Scandinavia, 

 which raised the various strata, and left them dipping to 

 the south-east. Worn down by denudation the edges 

 are now exposed in lines running south-west to north-east, 

 while the strata dip south-east under the edges of the 

 more recent strata. The Lias is noted for its ammonites, 

 and especially for its great marine reptiles, Ichthyosaurus 

 and Plesiosaurus. The Oolitic Epoch follows a long 

 period during which the fine limestone, the Bath freestone, 

 was made ; the limestones of the Cotswolds, beds of clay 

 known as the Oxford and Kimmeridge clays ; and again 

 coral reefs left the rock known as coral rag. In the later 

 part of the period were formed the Portland and Purbeck 

 beds, marine and freshwater limestones, which contain 

 also an old land surface, which has left silicified trunks of 

 trees and stems of cycads. 



And now following on these came our Wealden strata, 

 the beginning of the Cretaceous period. You see what 

 ages and ages had gone before, and that when Wealden 

 times came, far back as they are, the world's history was 

 comparatively approaching modern times. We must 

 remember that all these formations, of which we have 

 given a rapid sketch, are of great thickness, thousands 

 of feet of rock, and represent vast ages of time. See 

 what we have got to from looking at the shells in the sea 

 cliff ! We have come to learn something of the world's 

 old history. We have been carried back through ages 

 that pass our imagination to the world's beginning, to the 

 time of the molten globe, before ever it was cool enough 

 to allow life we know not how to begin upon its 



