1813J On Formations. ' 20B 



cabinet also one of comparative osteology. As his t^icws m 

 geognosy enlarged, be saw more and more the value of i h :- 

 and deep study of petrifactions. He first m^;-e 

 important observation, that different formation? c?. V j v 

 nated by the petrifactions they contain. It was q^; y : 

 of bis geognostical investigations that be ascertained 

 distribution of organic remains in the crust of the car 

 found that petrifactions appear first in transition rock;. , s i 

 are but few in number, and of animals ot the zoopliytl r 

 testaceous kinds. In the older tloetz rocks tliey are of mere 

 perfect animals ; and in the newest floetz and alluvial rocks, of 

 birds and quadri'peds, or animals of the most perfect kinds. He 

 also found that the oldest vegetable petrifactions were of marine 

 plants, the newer of large trees. 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 tlie genera or species of the present 

 time : that the newer the formation the more do the rem;iir;3 

 approach in form to the organic beings of tliC present cre;uif>n, 

 and that in the very nevv^est formations fossil remaiiis of tlie 

 present existing species occur. He also ascertained that the 

 petrifactions in the oldest rocks were much more mineralised 

 than the petrifactions in the newer rocks, and that in the newest 

 rocks they were merely bleached or calcined. He found that 

 some species of petrifactions were confined to particular beds, 

 others w^ere distributed throughout whole formations, and others 

 seemed to occur in several different formations ; the original 

 species found in these formations appearing to have been so 

 constituted as to live through a variety of changes which had 

 destroyed thousands of other species, which we find confined to 

 particular beds. He ascertained the existence of fresh water 

 shells in solid strata, sometimes alone, sometimes inteiinixed 

 with marine productions. These highly interesting observations- 

 having become gemrk\]y known by means of his pupils, gave a 

 stimulus to the study of petrifactions, which in a few years pro- 

 duced important results. They attracted the particular attention 

 of the mineralogist, and roused the curiosity of the zoologist and 

 botanist. They saw before them a wide field of the most inte- 

 resting nature. Tlie mineralogist confidently anticipated from 

 this study im.portant elucidations in regard to the various changea 

 the earth has undergone, dL5ring the progress of its formation, 

 from^the earliest periods to the present time. The zoologist and 

 botanist, by the discovery of new genera and species, hoped to 

 increase the number of natural families, to fill up gaps in the 

 present systems, and thus to perfect more and more the natural 

 system of animals and plants. But this was not all. The 

 philosophic naturalist soon iavv,- that these investigations would 



