232 PROGRESS OF SCIENCE IN THE CENTURY. 



of " whinstone " and the like, the idea of the meta- 

 morphism of rocks under the influence of new condi- 

 tions, and the doctrine of earth-sculpture by denuda- 

 tion (through rain, rivers, glaciers, etc.). 



Neptunists and Plutonists. The masterly and 

 lucid Illustrations of the Huttonian Theory by 

 Hutton's friend and disciple John Playfair, did 

 much to help the new theory of the earth towards 

 acceptance. But this was further delayed by the 

 bitterness of the strange controversy which sprang 

 up between Hutton's followers nicknamed Plu- 

 tonists and those of Werner, who were similarly 

 called Neptunists. Hutton had emphasised the im- 

 portance of subterranean heat in consolidating and 

 upheaving sedimentary deposits ; Werner had almost 

 exclusively emphasised the agency of water, believ- 

 ing that the rocks had arisen for the most part as 

 precipitates in a primeval ocean. To one looking 

 backward it does not seem an instructive controversy, 

 and it is perhaps enough to say that the more stable 

 doctrines of Hutton were those that survived. 



Hall. The Neptunists had urged against the Plu- 

 tonists that if basalt and the like had really arisen 

 from molten masses, they ought to be found as glasses 

 or slags. To this Sir James Hall retorted by ex- 

 periment, showing that basalt could be fused and 

 vitrified, and that if a portion of this basalt-glass was 

 re-fused and allowed to cool very slowly, it resumed 

 its familiar stony textures. From pounded chalk, 

 fused under pressure, he obtained a substance resem- 

 bling marble. In another direction he also experi- 

 mented most suggestively, for he arranged a mechan- 

 ical device for contorting layers of clay (by lateral 

 compression under considerable vertical pressure), 

 and showed that the foldings of strata could thus be 



