§ 60. CONCLUDING REMARKS. 289 



that the melting and transmutation of loose materials into 

 compact rocks, the conversion of incoherent strata into 

 solid stone, and even the sublimation of gold and other 

 metals into fissures and veins, are phenomena which have 

 taken place since our seas were peopled by mollusca of 

 existing species. The importance of these extraordinary 

 and interesting facts will be rendered more obvious in a 

 subsequent lecture. 



60. Concluding remarks. — In conclusion, it will be 

 useful to inquire, even though some repetition may be 

 incurred, what are the legitimate inferences from the facts 

 that have been placed before us, as to the condition of our 

 globe and its inhabitants during the tertiary epoch ? Was 

 there, as some have supposed, an essential difference in the 

 constitution of the earth ? — was its surface more covered 

 with lakes and marshes than now ? — and did animal life 

 more abound in those types, which are suitable to a lacus- 

 trine condition ? — or have such conclusions been drawn 

 from a partial view of the phenomena, and do the facts only 

 warrant the inference, that certain regions which are now 

 dry land, were in ancient times submerged beneath the sea, 

 or covered by vast lakes ; and that there may have existed 

 contemporaneously, as great an extent of dry land as at 

 present, in areas now buried beneath the ocean ? — In the 

 fossilized remains of the population of the tertiary lands and 

 waters, we find all the grand types of the existing faunas — 

 terrestrial, lacustrine, and marine mammalia — herbivora, 

 carnivora, birds of every order, and of numerous species 

 and genera — reptiles, fishes, Crustacea, insects, zoophytes, 

 and even those living atoms, the infusoria — in short, all 

 the leading divisions, and subdivisions of the animal 

 creation. In the vegetable world the same general analogy 

 is maintained ; and as all these varied forms of being 

 required corresponding physical conditions, we have at once 

 conclusive evidence that the general constitution of the earth, 



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