INTRODUCTION. 71 



ancient faunas assumes an abundant vegetation, and direct 

 evidence of extinct floras is presented in the coal and 

 bituminous deposits of the Carboniferous and other epochs. 

 Other evidence is afforded in the silicified trunks of trees that 

 occasionally are found in marine deposits, and have clearly 

 been swept into the sea from adjacent lands. 



Hutton then sets forth, in passages that have become classic 

 in geological science, the slow processes of the subaerial denuda- 

 tion of land-surfaces. He describes the effects of atmospheric 

 weathering, of chemical decomposition of the rocks, of their 

 demolition by various causes, and the constant attrition of the 

 soil by the chemical and mechanical action of water. He 

 elucidates with convincing clearness the destructive physical, 

 chemical, and mechanical agencies that effect the dissolution 

 of rocks, the work of running water in transporting the worn 

 material from the land to the ocean, the steady subsidence of 

 coarser and finer detritus that goes on in seas and oceans, lakes 

 and rivers, and the slow accumulation of the deposits to form 

 rock-strata. Hutton impresses upon his readers the vastness 

 of the geological seons necessary for the completion of any 

 such cycle of destruction and construction. In proof of this, 

 he calls attention to the comparative insignificance of any 

 changes that have taken place in the surface conformation of 

 the globe within historic time. 



Hutton was thus the great founder of physical and dynamical 

 geology; he for the first time established the essential correla- 

 tion in the processes of denudation and deposition; he showed 

 how, in proportion as an old continent is worn away, the 

 materials for a new continent are being provided, how the'' 

 deposits rise anew from the bed of the ocean, and another land j 

 replaces the old in the eternal economy of nature. The out-/ 

 come of Hutton's argument is expressed in his words {C that wej 

 find no vestige of a beginning, no prospect of an end." 



When we compare Hutton's 'theory of the earth's structure 

 with that of Werner and other contemporary or older writers, 

 the great feature which distinguishes it and marks its superiority, 

 is the strict inductive method applied throughout. Every! 

 conclusion is based upon observed data that are carefully' 

 enumerated, no supernatural or unknown forces are resorted to, 

 and the events and changes of past epochs are explained from 

 analogy with the phenomena of the present age. 



The undeveloped state of physics and chemistry in the time 



