240 THE STOKY OP THE EARTH AND MAN. 



by the difficulty that as the continents have retained 

 their present forms and characters to a great extent 

 throughout this time, we fail to find those evidences 

 of long- continued submergences of the whole conti- 

 nental plateaus, or very large portions of them, which 

 we have found so very valuable in the Palaeozoic and 

 Mesozoic. In the Eocene, however, we shall discover 

 one very instructive case in the great Nnmmulitic 

 Limestone. In the Miocene and Pliocene the oscilla- 

 tions seem to have been slight and partial. In the 

 Post-pliocene we have the great subsidence of the 

 glacial drift; but that seems to have been a compara- 

 tively rapid dip, though of long duration when mea- 

 sured by human history; not allowing time for the 

 formation of great limestones, but only of fossiliferous 

 sands and clays, which require comparatively short 

 time for their deposition. If then we ask as to the 

 duration of the Neozoic, I answer that we have not a 

 definite measure of its ages, if it had any ; and that it 

 is possible that the Neozoic may have as yet had but 

 one age, which closed with the great drift period, and 

 that we are now only in the beginning of its second 

 age. Some geologists, impressed with this compara- 

 tive shortness of the Tertiary, connect it with Meso- 

 zoic, grouping both together. This, however, is 

 obviously unnatural. The Mesozoic time certainly 

 terminated with the Cretaceous, and what follows 

 belongs to a distinct aeon. 



But we must now try to paint the character of this 

 new and peculiar time ; and this may perhaps be best 



