﻿IXX PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



birds have been derived. But if we remain so ignorant of the inha- 

 bitants of caverns in all the tertiary periods except the latest, how 

 little knowledge can we expect to derive from a similar source 

 respecting the terrestrial fauna, when we carry back our inquiries 

 to the Wealden or Carboniferous epochs ! We are as well assured 

 that land and rivers then existed, as that they exist now ; but it is 

 evident that even a slight geographical revolution or transference 

 of the position of land and sea tends rapidly to diminish our chances 

 of learning what mollusca or mammalia may then have inhabited 

 the land. 



Yet, small as may be the progress hitherto made in deciphering 

 the records of the tertiary periods, we seem entitled to declare that 

 during several great revolutions in the mammalia, probably not less 

 than five, there has been no step whatever made in advance, no ele- 

 vation in the scale of being ; so that, had man been created in the 

 lower eocene era, he would not have constituted a greater innova- 

 tion on the state of the animate creation previously established, than 

 now, when we believe him to have begun to exist at the close of the 

 pliocene. 



Antecedently to investigation, we might reasonably have anticipated 

 that the vestiges of man would have been traced back at least as far 

 as those modern strata in which all the testacea and a certain number 

 of the mammalia are of existing species, for of all the mammalia 

 the human species is the most cosmopolite, and perhaps more capable 

 than any other of surviving considerable vicissitudes in climate and 

 in the physical geography of the globe. How far the interior of 

 Asia, the supposed cradle of our race, may hereafter afford geological 

 evidence of higher antiquity than can be deduced from European 

 monuments, we have yet to learn. The observations recently made 

 by Dr. Abich on the changes of level going on in the Caspian ; the 

 periodical oscillations of level in that sea, due principally to subter- 

 ranean movements ; the shifting of the position of its waters, partly 

 by the encroachment of deltas on one side and the overflowing of the 

 land in other directions; the buildings now seen under water while others 

 are above the sea-level, and yet, like the temple of Serapis, having 

 been drilled by perforating mollusks, bear the marks of former sub- 

 mergence — these proofs of recent changes, coupled with the evidence 

 obtained by MM. Murchison and De Verneuil, of the vast extent 



