294 SCIENTIFIC THOUGHT. 



on foot without the guidance of previous observers or 

 the aid of fellow - labourers," l and "had thus singly 

 effected for the whole of England what many celebrated 

 mineralogists had only accomplished for a small part of 

 Germany in the course of half a century." 5 Simultane- 

 ously with Smith in England, Cuvier and Brongniart were 

 exploring the Paris basin. Thus the three different 

 nations of Europe with whom I am mainly concerned 

 in this work furthered independently the main divisions 

 of geological inquiry. "The systematic study of what 

 may be called mineralogical geology had its origin in 

 Germany, where Werner first described with precision 

 the mineral character of rocks ; the classification of the 

 secondary formations belongs to England, where the 

 labours of Smith were steadily directed to these ob- 

 jects ; the foundation of the third branch, that relating 

 to the tertiary formation, was laid in France by the 

 splendid work of Cuvier and Brongniart." 3 To these 

 words of Lyell we can now add that the theoretical 

 explanations were first suggested, and the correct line 

 of reasoning on this accumulated evidence initiated, by 

 Sir Charles Lyell himself. 



The key to the doctrines of Lyell was the study of 

 existing causes the attempt to show how the slow 

 agencies which we now see at work in nature around 

 us are sufficient to explain the successive changes 4 



1 Lyell, ' Principles,' vol. i. p. only by carefully considering the 



combined action of all the causes of 

 change now in operation, whether 

 in the animate or inanimate world, 

 that we can hope to explain such 

 complicated appearances as are ex- 

 hibited in the general arrangement 



101. 



2 An expression of d'Aubuisson, 

 quoted by Dr Fitton, ' Phil. Mag.,' 

 vols. i. and ii., also ; Edin. Rev.,' 

 Feb. 1818. 



3 See Lyell, loc. tit., p. 103. 



4 Id. ibid., vol. iii. p. 273 : "It is ' of mineral masses." 



