THE GROWTH OF BRITAIN 213 



the succession of Jurassic and Cretaceous Rocks was folded and 

 exposed to denudation, so that their wolds and downs are the 

 result of the denudation of the folded rocks (Figs. 51, 64, and 66). 

 Thus the main features of eastern and southern England date to 

 this period. Connected with the movement are the volcanic 

 rocks of the Inner Hebrides, the result of a tremendous outburst 

 of energy in these regions, the effects of which spread far and 

 wide in the intrusion of dykes and sheets of igneous rocks as far 

 south as the Land's End, as far east as the Yorkshire coast, and as 

 far west as Donegal. 



Deposits of Miocene age, the height of the movement, are 

 wanting in Britain, but on the continent they recall curiously the 

 character of such terrestrial deposits as the Old and New Red 

 Sandstones. In this country no deposits appear to have been 

 made, or what may have been formed were afterwards destroyed, 

 but strata of older date were folded and overthrust as the 

 consequence of the movement. 



Thus the landscape of our country is found to be the outcome 

 of two great processes. The deposition of marine strata with their 

 fossils and other characteristics during periods of rest and quiet ; 

 and the elevation and folding of the rocks so formed during 

 periods of activity in the earth-crust. The landscape does not 

 depend upon a single epoch of deposition or denudation, but is 

 the result of several periods of each class of activity, and it may be 

 said to have been slowly evolved by the interaction of the two 

 processes. The older strata and the landscape dependent on 

 them may have had very different levels and may have been 

 influenced by the different types of denudation resulting from 

 each of them. Thus many parts of the landscape are ancient, 

 others have been rejuvenated, others again are in their first 

 juvenile stage. But all bear out the great principle of evolution 

 which is applicable to the geography, the landscape, and indeed 

 the climate of the country, as much as to its populations of animals 

 or plants. 



The occurrence of an Alpine plant in a Welsh mountain re- 

 quires not only the explanation that it is a survival of an Arctic 

 flora which occupied the country in Glacial times. It requires 

 that geographical conditions should have been favourable during 



