THEORY OP THE EARTH. 117 



ceeding formations. Ancient formations may have 

 been transported into new situations by means of 

 partial inundations, and may thus have covered 

 over recent formations containing bones; they 

 may have been carried over by debris so as to sur- 

 round these recent bones, and may have mix- 

 ed with them the productions of the ancient sea, 

 which they previously contained. Anciently de- 

 posited bones may have been washed out from 

 their original situations by the waters, and been 

 afterwards enveloped in recent alluvial formations. 

 And, lastly, recent bones may have fallen into the 

 crevices and caverns of ancient rocks, where they 

 may have been covered up by stalactites or other 

 incrustations. In every individual instance, there- 

 fore, it becomes necessary to examine and appre- 

 ciate all these circumstances, which might other- 

 wise conceal the real origin of extraneous fossils; 

 and it rarely happens that the people who found 

 these fossil bones were aware of this necessity, and 

 consequently the true characters of their reposi- 

 tories have almost always been overlooked or mis- 

 understood. 



Thirdly, there are still some doubtful species of 

 these fossil bones, which must occasion more or less 

 uncertainty in the result of our researches, until 

 they have been clearly ascertained. Thus the fos- 

 sil bones of horses and buffaloes, which have been 

 found along with those of elephants, have not hi- 

 therto presented sufficiently distinct specific cha- 



