21$ NATURAL HISTORY 



during the course of his geognostical investigations thai 

 he ascertained the general distribution of organic remains 

 in the crust of the earth. He found that petrifactions 

 appear first in transition rocks. These are but few in 

 number, and of animals of the zoophytic or testaceous 

 classes. In the older flretz rocks they are of more per- 

 fect species, as of fish and amphibious animals ; and in the 

 newest floetz and alluvial rocks, of birds and quadrupeds, 

 or animals of the most perfect kinds. He always main- 

 tained that no fossil remains of the human species had been 

 found in floetz rocks, or in any of the older alluvial for- 

 mations ; but was of opinion that such remains might be 

 discovered in the very newest of the alluvial depositions. 

 He was also led to believe, from his numerous observa- 

 tions, that sea plants were of more ancient origin than 

 land plants. A careful study of the genera and species of 

 petrifactions disclosed to him another important fact, 

 viz, that the petrifactions contained in the oldest rocks 

 are very different from any of the species of the present 

 time ; that the newer the formation, the more do the re- 

 mains approach in form to the organic beings of the pre- 

 sent creation ; and that in the very newest formations, 

 fossil remains of the presently existing species occur. 

 He also ascertained, that the petrifactions in the oldest 

 rocks are much more mineralized than those in the newer 

 rocks, and that in the newest rocks they are merely 

 bleached or calcined. He found that some species of 

 petrifaction were confined to particular beds ; others 

 were distributed throughout whole formations, and others 

 seemed to occur in several different formations ; the ori- 

 ginal species found in these formations appearing to 

 have been so constituted as to live through a variety of 

 changes which had destroyed hundreds of other species, 

 which we find confined to particular beds. 



