PREFACE. 



exceedingly rare to find a species common to two beds, al- 

 though they lie in juxtaposition ; or one may repose upon the 

 other. Hence, the utility of the presence of fossils to distin- 

 guish beds belonging to the different epochs from each other. 

 Another object which I had in view in occupying so much 

 space upon this subject, was, to aid those who wish to become 

 acquainted with this interesting subject. Geology is* now 

 commanding the attention of some of the best minds in this 

 country and Europe. It is invested with great importance 

 and interest, as it is through the discoveries in this depart- 

 ment of science, that we obtain a knowledge of the ancient 

 history of the globe. This pursuit is especially recommended 

 to the attention of the young. It will be found extremely 

 interesting and useful, and no one will regret afterwards that 

 he devoted a portion of his leisure hours to its study. 





