SYSTEMATIC DESCRIPTIVE GEOLOGY. 553 



system "filled him with delight, and called forth 

 such marks of joy and exultation, that the guides 

 who accompanied him were persuaded, says his 

 biographer 13 , that he must have discovered a vein of 

 silver or gold 14 ." 



Desmarest's examination of Auvergne (1768), 

 showed that there was there an instance of a 

 country which could not even be described without 

 terms implying that the basalt, which covered so 

 large a portion of it, had flowed from the craters of 

 extinct volcanoes. His map of Auvergne was an 

 excellent example of a survey of such a country, 

 thus exhibiting features quite different from those 

 of common stratified countries 15 . 



The facts connected with metalliferous veins 

 were also objects of Werner's attention. A know- 

 ledge of such facts is valuable to the geologist as 

 well as to the miner, although even yet much diffi- 

 culty attends all attempts to theorize concerning 

 them. The facts of this nature have been collected 

 in great abundance in all mining districts; and 

 form a prominent part of the descriptive geology 

 of such districts ; as, for example, the Hartz, and 

 Cornwall. 



Without further pursuing the history of the 

 knowledge of the inorganic phenomena of the earth, 

 I turn to a still richer department of geology, which 

 is concerned with organic fossils. 



1S Playfair's Works, vol. iv. p. 75. " Lyell, i. 90. 



15 Lyell, i. 86. 



