S98 Observations cm the Nature and Importance ofGeohgy, 



of animal remains, but few belong to species now living, and 

 these only, in the most recent rock-formations ; by far the great- 

 er number of their primitive structures are lost, and the older 

 the beds of rock in which they make their appearance, so much 

 the more do they deviate in their formation from the species now 

 in existence. May this destruction, as is commonly received, 

 have been the^result of violent accidents, and destructive revo- 

 lutions of the earth ; or does it not rather indicate a great law of 

 nature, which cannot be discovered by reason of its remote an- 

 tiquity ? Within the narrow circle of vision in which the organic 

 world manifests itself to our observation, we observe individuals 

 only going to destruction, and in opposition to that, great pre- 

 parations making for the preservation of the species. But if all 

 living perish, may no point of duration have been fixed for the 

 species ; or do we not rather, in these signs of a former world, 

 discover a proof, that, from a change in the media in which or- 

 ganic creatures lived, and from powerful causes operating upon 

 them, their power of propagation may be weakened, and at 

 length become perfectly extinct ? Is the continual decrease, then, 

 which we observe among some species, a consequence of the va- 

 rious modes of destruction they experience from the hand of 

 man, or may it not rather be produced by natural circumstan- 

 ces, and be a sign of the approaching old age of the species ? 



The distinction of species is undoubtedly one of the founda- 

 tions of natural history, and her character is the propagation of 

 similar forms. But are these forms as immutable as some dis- 

 tinguished naturalists maintain ; or do not our domestic animals 

 and our cultivated or artificial plants prove the contrary ? If 

 these, by change of situation, of chmate, of nourishment, and 

 by every other circumstance that operates upon them, can change 

 their relations, it is probable that many fossil species to which 

 no originals can be found, may not be extinct, but have gra- 

 dually passed into others. As there are periodical movements 

 of the heavenly bodies, that is, movements that are visible only 

 after hundreds of years, so these are undoubtedly periodical 

 changes in the organic world. If these have required intervals 

 of time that are antecedent to all historical traditions, and to the 

 duration even of the human race, the monuments concealed in 



