ORIGIN OF SCENERY 193 



movements which from time to time have convulsed 

 the earth, their details of contour must be mainly due 

 to the eroding power of running water. They recog- 

 nised that as the surface of the land is continually worn 

 down, it is essentially by a process of sculpture that 

 the physiognomy of every country has been developed, 

 valleys being hollowed out and hills left standing, and 

 that these inequalities in topographical detail are only 

 varying and local accidents in the progress of the one 

 great process of the degradation of the land. 



From the broad and guiding outlines of theory 

 thus sketched we have now advanced amid ever- 

 widening multiplicity of detail into a fuller and nobler 

 conception of the origin of scenery. The law of evo- 

 lution is written as legibly on the landscapes of the 

 earth as on any other page of the Book of Nature. 

 Not only do we recognise that the existing topography 

 of the continents, instead of being primeval in origin, 

 has gradually been developed after many precedent 

 mutations, but we are enabled to trace these earlier 

 revolutions in the structure of every hill and glen. 

 Each mountain-chain is thus found to be a memorial 

 of successive stages in geographical evolution. Within 

 certain limits, land and sea have changed places again 

 and again. Volcanoes have broken out and have 

 become extinct in many countries long before the 

 advent of man. Whole tribes of plants and animals 

 have meanwhile come and gone, and in leaving their 

 remains behind them as monuments at once of the 

 slow development of organic types, and of the pro- 

 longed vicissitudes of the terrestrial surface, have fur- 

 nished materials for a chronological arrangement of 



