50 THEORY OF THE EARTH. 



through all their defiles; has laid open to our 

 view the entire disorder of the primitive forma- 

 tions, and has distinctly traced the limits by which 

 they are distinguished from the secondary forma- 

 tions. The other, taking advantage of the nu- 

 merous excavations made in the most ancient min- 

 ing district in the world, has fixed the laws by 

 which the succession of the strata are regulated, 

 pointing out the relative antiquity of these stra- 

 ta, and tracing each of them through all its me- 

 tamorphoses. It is from him, and from him alone, 

 that we date the commencement of real geo- 

 logy, in so far as concerns the mineral nature of 

 the strata : but neither he nor Saussure have de- 

 termined the fossil organic species occurring in 

 each kind of stratum, with the accuracy which 

 has become necessary, now that the number of 

 animals already known is so great. 



Other naturalists, it is true, have examined the 

 the fossil remains of organised bodies ; they have 

 collected and figured them by thousands, and 

 their works will serve as so many precious collec- 

 tions of materials. But, considering these ani- 

 mals and plants more with reference to their own 

 nature, than as connected with the theory of the 

 earth ; or regarding these petrifactions as cu- 

 riosities, rather than as historical documents ; or, 

 lastly, contenting themselves with practical ex- 

 planations regarding the position of each frag- 



