1 70 The Founders of Geology LECT. 



materials of sedimentary strata, nor how much may be 

 done by infiltration and deposition between the clastic 

 grains. But there was one effect of compression which, 

 though not perhaps at first sight obvious, was clearly 

 perceived by him in its geological relations. He saw that 

 the influence of heat upon rocks must be largely modified 

 by pressure. The more volatile components, which would 

 speedily be driven off by a high temperature at the surface, 

 may be retained under great pressure below that surface. 

 Hutton conceived that limestone might even be fused in 

 this way, and yet still keep its carbonic acid. This idea 

 was ridiculed at the time, but its truth was confirmed 

 afterwards by Hall's experiments, to which I shall allude 

 in a later part of this lecture. 



The next step in his reasoning was that whereby 

 Hutton sought to account for the present position of the 

 strata which, originally deposited under the sea, are now 

 found even on mountain crests 15,000 feet above sea-level. 

 We have seen how Werner looked on his vertical primitive 

 strata as having been precipitated from solution in that 

 position, and as having been uncovered by the gradual 

 subsidence and disappearance of the water. Hutton 

 attacked the problem in a very different fashion. He saw 

 that if the exposure of the dry land were due merely to the 

 subsidence of the sea, it would involve no change in the 

 positions of the strata relatively to each other. What were 

 first deposited should lie at the bottom, what were last 

 deposited at the top ; and the whole should retain their 

 original flatness. 



But the most cursory examination was, in his opinion, 

 sufficient to show that the actual conditions in nature 



