INVESTIGATION OF TEMPERATURE CHANGES. 253 



the Miocene epoch ; for, so far ns known at the present time, there was noth- 

 ing of the kind existing in Pliocene times. Moreover, the gradual refrigera- 

 tion of Europe from the Miocene epoch on becomes very marked, although 

 in certain localities the Pliocene flora has still the characters indicative of 

 a considerably warmer climate than that which now prevails in the same 

 region. Thus the rich Pliocene flora of Meximieux, not far from Lyons, 

 proves the climatic conditions at that point to have been analogous to those 

 now prevailing in the Canary Islands. Similar facts are reported from the 

 volcanic region of Central France, in the Cantal, where recent explorations 

 have revealed the presence of a flora, imbedded beneath the basaltic rocks, 

 and belono-imr to the same horizon as that of Meximieux. 



o o 



It seems hardly necessary to bring- forwai'd farther evidence of the preva- 

 lence of a warmer climate in former geological ages ; this seems to have 

 been clearly enough demonstrated by what has already been stated in the 

 preceding pages. Indeed, that such a refrigeration has taken place is ad- 

 mitted b}^ geologists, almost without exception. That the proofs of this 

 should come, in by far the larger part, from the northern hemisphere, and 

 also from Europe and North America, is not at all surprising. It is there 

 that much the larger portion of the accurate work has been done by which 

 the histor}^ of the past has been revealed to the inquirer in this department 

 of investigation. As yet, we hardly know more than the merest outlines of 

 the geological structure of either Asia, Africa, or South America. The forms 

 of the land masses must also be taken into consideration in this connection. 

 The extension of the ocean over by far the larger portion of the southern 

 hemisphere, the almost entire inaccessibility of the Antarctic continent, 

 and the comparatively small amount of exploration which has been done 

 along its borders, — these are sufficient reasons why no proof-* of the former 

 prevalence of a warmer climate at the South pole could be expected to be 

 given. Certainly nothing of that kind is possible at the present time, nor 

 does there seem to be much encouragement that such evidence will be fur- 

 nished in the immediate future. 



It will, very probabl}-, be thought by some that the Avriter has passed over 

 in silence facts which indicate, if they do not prove, that there have been 

 recurrences of periods of cold during the geological epochs ; and perhaps it 

 will seem to some that he has omitted to brinsr forward evidence of a similar 

 kind favoring the popular idea of amelioration of the climate — of certain 

 regions, at least — during the historic j^eriod. The theory of the alternation 



