SYSTEMATIC DESCRIPTIVE GEOLOGY. 515 



author of the theory of igneous causation which was in this <ountry 

 opposed to that of Werner, sought and found this phenomenon in the 

 Grampian hills, in 1785. This supposed verification of his system 

 " filled him with delight, and called forth such marks of joy and exul- 

 tation, that the guides who accompanied him were persuaded, says his 

 biographer, 13 that he must have discovered a vein of silver or gold."' 



Desmarest's examination of Auvergne (1768) showed that there was 

 there an instance of a country which could not even be described with- 

 out 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 knowledge of such facts is valuable to the 

 geologist as well as to the miner, although even yet much difficulty 

 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 inor- 

 ganic phenomena of the earth, I turn to a still richer department of 

 geology, which is concerned with organic fossils. 



Sect. 3. Application of Organic Remains as a Geological Character. 



Smith. 







ROUELLE and Odoardi had perceived, as we have seen, that fossils were 

 grouped in bands : but from this general observation to the execution 

 of a survey of a large kingdom, founded upon this principle, would 

 have been a vast stride, even if the author of it had been aware of the 

 doctrines thus asserted by these writers. In fact, however, William 

 Smith executed such a survey of England, with no other guide or help 

 than his own sagacity and perseverance. In his employments as a 

 civil engineer, he noticed the remarkable continuity and constant order 

 of the strata in the neighborhood of Bath, as discriminated by their 

 fossils ; and about the year 1793, he 14 drew up a Tabular View of the 



" Play fair's Works, vol. iv. p. 75. J4 Lyell, i. 90. 



" Lyell, i. 86. M Fitton, p. 148. 



