138 



MIOCENE CLIMATE. 



European and North-American types become more prominent. 

 If the living species most like the Swiss Miocene plants are 

 distributed into three zones, we obtain the following numerical 

 proportions : 



In the Upper Miocene (of CEningen) the tropical types con- 

 stitute only 7 per cent, of the total number of vascular plants; 

 whilst in the lower Miocene (Aquitanian) the tropical types are 

 15 per cent, of the whole, which shows that a decrease of tem- 

 perature must have taken place, although the frequent occur- 

 rence of the camphor- and cinnamon-trees, and the appearance 

 of feather- and fan-palms, demonstrate that CEningen still 

 enjoyed a warm climate. 



If we sum up all the data furnished by the flora, we are led 

 to the conclusion that the Swiss Lower Miocene district pos- 

 sessed a climate similar to that now prevailing in Louisiana, 

 the Canaries, North Africa, and South China namely, a climate 

 with a mean annual temperature of 20-21 Cent, (or 68-69'8 

 Fahr.); and that the Swiss Upper Miocene district had a 

 climate resembling that of Madeira, Malaga, and the south of 

 Sicily, Southern Japan, and New Georgia, with an annual 

 temperature of 18-19 Cent, (or 64'4-66 *2 Fahr). 



The following Table gives the mean temperatures of the 

 above-mentioned regions : 



