506 A. Blytt on the probable Cause of 



During the Eocene it rose again, and the Eocene sea had a 

 great extension ; we find its formations even in the heart of 

 Upper Asia. The limit between the Eocene and OKgocene is 

 again distinguished by a negative phase. In the latter part 

 of the Oligocene period, and still more during the Miocene, 

 the sea again rose ; between the Miocene and Pliocene it 

 retreated far, and at the beginning of the Quaternary epoch 

 it rose again. Similar great oscillations are also to be traced 

 in North America and in Patagonia. But marine Miocene 

 deposits are wanting in the last-mentioned locality, where the 

 Miocene freshwater beds are associated with great quantities 

 of volcanic products. 



At the commencement of the Tertiary period, when the sea 

 had retreated far under high latitudes, the climate of Europe 

 was temperate rather than tropical (see Saporta, Le Monde des 

 Plantes avant Vapparition de P/iomme, 1879). According as 

 the sea rose, and the Eocene overflow advanced, the climate 

 became warmer ; and at the close of the Eocene period the 

 climate of Southern Europe was hot and dry. The abundant 

 Tertiary flora of the Arctic lands is (according to Saporta and 

 Gardner) rather Eocene than Miocene (as Heer supposed). 

 At the boundary between Eocene and Oligocene the sea 

 retreated, and the Arctic Tertiary flora began to migrate into 

 Europe, supplanting the more southern plants. Then came 

 the Miocene overflow, and with it a rich tropical or subtro- 

 pical flora. But in proportion as the Miocene sea retreated, the 

 European flora also, little by little, lost in richness and beauty, 

 and the tropical elements became more and more rare. During 

 the Pliocene epoch the sea retreated still further, and the 

 climate became colder and colder until the Glacial period 

 came in. But the last Quaternary overflow has again, 

 after several oscillations, caused the ice to retreat, and our 

 climate has again become temperate. There is thus clearly a 

 relation of dependency between the climate and geographical 

 conditions. Great seas under high latitudes produce warm 

 chmates and vice versa. 



Now, we have seen that these great geographical changes 

 W'ere in all probability a consequence of the rising and sinking 

 of the mean value of the eccentricity ; and we must therefore 

 belicA^e that these great changes of the climate had a cosmical 

 origin, and occurred at the same time over the A\hole earth. 

 We still know too little of the geology of trojical countries; 

 but there is ground for the belief that here also great changes 

 have taken place in the distribution of land and sea, and that 

 these changes must also have had an influence upon the 

 climate of the warm countries. 



