THE NORTHERN VEGETATION COMPARED, ETC. 151 



and fauna of North America, and the fossils of the miocene period 

 in Europe, would also give a valuable hint with respect to the mean 

 annual temperature of that geological period. 



Oenlngen, for instance, whose fossils of all classes have perhaps 

 been more fully studied than those of any other locality, could not 

 have enjoyed during that period a tropical or even a sub-tropical cli- 

 mate, such as has often been assigned to it, if we can at all rely upon 

 the indications of its flora, for this is so similar to that of Charleston, 

 South Carolina, that the highest mean annual temperature we can 

 ascribe to the miocene epoch in Central Europe must be reduced to 

 about 60° Fah. ; that is to say, we infer from its fossil vegetation that 

 Oeningen had, during the tertiary times, the climate of the warm 

 temperate zone, the climate of Rome, for instance, and not even that 

 of the northern shores of Africa. We are led to this conclusion by 

 the following argument : — The same isothermal line which passes at 

 present through Oeningen at the 47th degree of northern latitude, 

 passes also through Boston, lat. 4:2°. Supposing now, (as the geolog- 

 ical structure of the two continents and the form of their respective 

 outlines at that period seem to indicate,) that the undulations of the 

 isothermal lines which we notice in our days existed already during the 

 tertiary period, or in other words, that the differences of temperature 

 which exist between the wesiprn shores of Europe and the eastern 

 shores of North America, were the same at that time as now, we shall 

 obtain the mean annual temperature of that age by adding simply the 

 difference of mean annual temperature which exists between Charles- 

 ton and Boston, (12° Fah.,) to that of Oeningen, which is 48° Fah., 

 as modern Oeningen agrees almost precisely with Boston, making it 

 60° Fah. ; far from looking to the northern shores of Africa for an 

 analogy, which the different character of the respective vegetations 

 would render still less striking. The mean annual temperature of 

 Oeningen during the tertiary period would not therefore differ more 

 from its present mean, than that of Charleston differs from that of 

 Boston. 



This old-fashioned look of the North American forests goes also to 

 show the intimate connection there is all over the globe between the 

 physical condition of any country, and the animals and plants pecuUar 



