Geology 



des Plantes, after which he became interested in miner- 

 alogy and, through its influence, in the wider problems of 

 Geology. 



He was the first to prepare a geological map, that is 

 to say, a map on which the distribution of the various 

 kinds of rocks and minerals is indicated. 



Guettard also added largely to the knowledge of 

 fossils, particularly of fossil sponges and corals, and it is 

 probably largely due to his labours that the great 

 palaeontological school of France came into being, and 

 that his countrymen are still pre-eminent in that domain 

 of science. 



At this period the science of mineralogy was much 

 in vogue. Minerals had long been studied from an 

 economic standpoint, and the term mineralogy was 

 then taken to include the study of rocks and their 

 contents. 



That the Earth's past history might be preserved in 

 the rocks and their fossils was an idea which appears to 

 have dawned upon Buffon, but was more fully realized 

 by Guettard, though he does not appear to have made 

 any definite observations in support of the view. 



Guettard had observed rocks which he believed to 

 be of volcanic origin in central France, far remote from 

 any active volcano, and from this discovery there 

 eventually resulted that greatest and most bitter of all 

 geological controversies regarding the origin of basalt. 



Nicholas Demarest, who was born in very poor 

 circumstances at a little town near Brienne, was destined 

 to play an important part in this great controversy. 



Such was the poverty of his parents that at the age 

 of fifteen he could hardly read, but on the death of his 



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