REPORT ON THE GEOLOGY OP NORTH AMERICA. 29 



It may seem at variance with what I have here advanced of 

 the recent and tranquil extinction of these animals, that in the 

 enormous accumulation of their relics at Big Bone Lick, the 

 boggy matter should be found partially filled with gravel, and 

 the larger bones universally fractured. However, the small 

 amount of gravel described as mingling with the peaty mass, 

 seems hardly to imply that this spot was visited at this time by 

 any violent action, such as covered the adjoining hills with their 

 boulders and gravel ; so that, on the whole, I am most inclined 

 to explain the fractured condition of the jaws, femora, &c., by 

 the constant treading and floundering of the huge animals over 

 the skeletons of their ancestors. 



Tertiary Formations. — Many circumstances tend to give 

 peculiar interest to the tertiary geology of America at the pre- 

 sent time. The day appears to have come when some of the 

 broad conclusions recently arrived at in Europe may be fitly 

 tested by a comparison with the phaenomena of remoter regions, 

 and America would seem to be so much dissociated from Eu- 

 rope, both by its insulated position and different physical struc- 

 ture, that the comparison between them will possess peculiar 

 weight. The great range which characterizes all the deposits 

 of America belongs, no less remarkably, to those of the tertiary 

 age, and affords a very favourable opportunity for ascertaining 

 to what extent formations so recent may be distributed 

 without departing materially from an uniform type, or where 

 they do depart, of determining the causes which influence the 

 variation. The existing animal and vegetable races of this 

 hemisphere differ so widely from those of the Old World, that 

 we are induced to inquire when, or whether at any time, the 

 species on the opposite sides of the Atlantic were more nearly 

 identical. These inquiries, bearing intimately on some of the 

 most important questions of the science, have been recently dis- 

 cussed with great ability by Mr. Lyell. I do not consider that 

 our researches have proceeded to a sufficient length to render 

 them of much weight upon many points in tertiary geology; but 

 I nevertheless venture to remark, that they will be found to af- 

 ford a striking corroboration of the soundness of the new prin- 

 ciple upon which the tertiary formations of Europe have been 

 arranged in chronological order by Lyell. They will perhaps 

 be seen at the same time to suggest some slight changes in the 

 views hitherto entertained respecting the different circumstances 

 under which tertiary and secondary groups are supposed to have 

 been severally formed. 



The area within which the tertiary deposits of this country 

 occur, so far as our information at present extends, is that por- 

 tion of the United States which I have styled the Atlantic 



