Page:Early Man in Britain and His Place in the Tertiary Period.djvu/90

62 streams of lava and clouds of ashes. In Switzerland also the formation of great lakes of upper Meiocene age was accompanied by the development of volcanoes, at Oeningen.

The central axis of the Alpine chain occupied its present position, and may have been as high or higher than it now is. The denudation, by which it has suffered in the long lapse of ages since the Meiocene times, has been compensated by the amount of elevation by which the Meiocene strata of the Tongrian zone have been lifted up no less than 10,940 feet above the sea in the Dent du Midi., Those of the Helvetian zone have been elevated 2470 feet at Lausanne, and 2800 at Berne.

The same remarks apply also to the Pyrenees, although their history has not been made out with the same accuracy as that of the Alpine chain.

The testimony as to climate offered by the Meiocene vegetation is clear and decisive. The numerous palms could only have flourished under a warm and equable climate, and the flora as a whole is now only to be found in sub-tropical regions, where the winters are very mild. In the vast lapse of time, however, represented by the Meiocene strata in Switzerland, a gradual lowering of temperature is marked by changes in the vegetation. In the lower Meiocene, or Aquitanian stage, evergreen trees and shrubs constitute nearly three-quarters of the whole forest, while in the upper Meiocene