50 Charles Schuchert — Historical Geology, 1818-1918. 



foundations of the earth. After a convulsion, there was 

 a long time of erosion, represented by the unconformity. 

 Geikie says, "The whole of the modern doctrine of 

 earth sculpture is to be found in the Huttonian theory. ' ' 



The Lyellian doctrine of metamorphism had its origin 

 in Hutton, for he showed that invading igneous granite 

 had altered, through its heat and expanding power, the 

 originally water-laid sediments, and that the schists of 

 the Alps had been born of the sea like other strati- 

 fied rocks. 



Hutton is the father of the Uniformitarian principle, 

 for he "started with the grand conception that the past 

 history of our globe must be explained by what can be 

 seen to be happening now, or to have happened only 

 recently. The dominant idea in his philosophy is that 

 the present is the key to the past." This principle has 

 been impressed on all later geologists by Sir Charles 

 Lyell, and is the chief cornerstone of modern geology. 



The principle of uniformitarianism has underlain 

 geologic interpretation since the days of Hutton, Play- 

 fair, and Lyell. However, it is often applied too rigidly 

 in interpretations based upon the present conditions, 

 because in the past there were long times when the topo- 

 graphic features of the earth were very different from 

 those of to-day. Throughout the Paleozoic, and, less 

 markedly, the Mesozoic, the oceans flooded the lands 

 widely (at times over 60 per cent of the total area), high- 

 lands were inconspicuous, sediments far scarcer, and cli- 

 mates warm and equable throughout the world. High- 

 land conditions, and especially the broadly emergent con- 

 tinents of the present, were only periodically present in 

 the Paleozoic and then for comparatively short intervals 

 between the periods. Therefore rates of denudation, 

 solution, sedimentation, and evolution have varied 

 greatly throughout the geological ages. These differ- 

 ences, however, relate to degrees of operation, and not to 

 kinds of processes ; but the differences in degree of 

 operation react mightily on our views as to the age of 

 the earth. 



Geologic time had, for Hutton, no "vestige of a begin- 

 ning, no prospect of an end." In other words, geologic 

 time is infinite. He did not, however, discover a method 

 by which the chronology of the earth could be determined. 



First Important Text-books. — In 1822 appeared the 



