GROWTH OF GEOLOGY. 231 



For the main purpose of this volume, which is to 

 illustrate the working of the scientific mood, the 

 theory of the earth which Hutton suggested is full 

 of significance. Significant, because its author had 

 so clearly grasped the scientific method of seeking to 

 appreciate the full force of known factors instead of 

 invoking the aid of others whose reality is hypotheti- 

 cal. Waters wear the stones, the solid earth melts 

 away, the mountain is transplanted piece-meal to the 

 sea, there is a ceaseless decay of continents; on the 

 other hand, underground forces cause upheaval, con- 

 solidated debris is once more brought to light, and 

 molten masses are here and there thrust upward to 

 form eruptive rock. What is, has been, and that 

 through a vast antiquity of ages, so that " little 

 causes, long continuing," have wrought great 

 changes. The present is the child of the past and the 

 parent of the future. In short it was the idea of 

 development that Ilutton had, perhaps subcon- 

 sciously, in mind. The keynote of his work may be 

 found in his sentence : ^' ilo powers are to be em- 

 ployed that are not natural to the globe, no action to 

 be admitted of except those of which we know the 

 principle, and no extraordinary events to be alleged 

 to explain a common appearance.'^ * 



Unlike Werner, Hutton started from observations 

 not from preconceptions. He studied the present, and 

 in the process now occurring found the key to the 

 history of the past. Among his conclusions we may 

 note : — The aqueous origin of sedimentary rocks, the 

 influence of subterranean force (essentially due to 

 heat) in contorting strata, the theory of subterranean 

 intrusions of molten matter forming veins or dykes 



* Theory of the Earth, Vol. II. p. 547. Quoted by Sir A, 

 Geikie, Founders of Geology, p. 182. 



