THE PRESENT KEY TO THE PAST 161 



stupendous internal force akin to that which gives 

 rise to the volcano and the earthquake. Hutton 

 further perceived that not only had the consolidated 

 sediments been disrupted and elevated, but that masses 

 of molten rock had been thrust upward among them, 

 and had cooled and crystallised in large bodies of 

 granite and other eruptive materials, which form so 

 prominent a feature on the earth's surface. 



As a further special characteristic, this philosophical 

 system sought, in the changes now in progress 

 on the earth's surface, an explanation of those which 

 occurred in older times. Its founder refused to 

 invent causes or modes of operation, for those with 

 which he was familiar seemed to him adequate to 

 solve the problems with which he attempted to deal. 

 Nowhere was the profoundness of his insight more 

 astonishing than in the clear, definite way in which 

 he proclaimed and reiterated his doctrine, that every 

 part of the surface of the continents, from mountain- 

 top to seashore, is continually undergoing decay, and 

 is thus slowly travelling to the sea. He saw that 

 no sooner will the sea-floor be elevated into new land 

 than it must necessarily become a prey to this universal 

 and unceasing degradation. He perceived that, as the 

 transport of disintegrated material is carried on chiefly 

 by running water, rivers must slowly dig out for them- 

 selves the channels in which they flow, and thus that 

 a system of valleys, radiating from the water-parting 

 of a country, must necessarily result from the descent 

 of the streams from the mountain crests to the sea. 

 He discerned that this ceaseless and widespread decay 

 would eventually lead to the entire demolition of the 



