68 THEORY OF THE EARTH. 



lebrated geologist, taking advantage of the nume- 

 rous excavations in the most ancient mining dis- 

 trict in the world, has fixed the laws which regu- 

 late the succession of strata, pointing out their 

 respective antiquity in regard to each other, and 

 tracing each of them through all its changes and 

 metamorphoses. From him alone we date the 

 commencement of real geology, so far as respects 

 the mineral natures of the strata : But neither he 

 nor Saussure has denned the species of organized 

 extraneous fossils in each description of the strata 

 with that accuracy which has become necessary, 

 now that the number of animals already known 

 has become so great. 



Other naturalists, it is true, have studied the fos- 

 . sil remains of organized bodies ; they have col- 

 lected and represented them by thousands, and 

 their works certainly will serve as a valuable 

 storehouse of materials. But, considering these 

 fossil plants and animals merely in themselves, in- 

 f stead of viewing them in their connexion with the 

 ' theory of the earth ; or regarding their netrifac- 

 tions and extraneous fossils as mere curiosities, 

 I rather than as historical documents ; or confining 

 themselves to partial explanations of the particular 

 bearings of each individual specimen ; they have 

 almost always neglected to investigate the general 

 laws affecting their position, or the relation of the 

 extraneous fossils with the strata in which they are 

 found. 



