10 Art. 5. — Matajiro Yokoyama : 



silice the earlier Pliocene, attaining its maximum in the Diluvial 

 and then again decreasing down to the present time. This is, as 

 every one can see, a state of things just the reverse of what we find 

 in Europe and America, a singular contrast for which there must 

 surely be a cause. 



But before entering into the discussion of this cause, let us go 

 back a little to the Miocene Epoch when Switzerland is said to 

 have enjoyed a climate such as we find now in the southernmost 

 cape of Kyushu (Sata-no-misaki in Osumi with a mean annual 

 temperature of 18°C) and Amami-Oshima (the northenmost of the 

 Ryukyu Islands with 20,8°C). The Japanese fauna of this epoch 

 has not yet been fuU}^ studied, but we know something of its 

 plants from the investigations of Nathorst.^' This palaeobotanist 

 found them to consist of a njixture of the European Miocene and 

 of the so-called Arctic-Tertiary flora, indicating that the climate 

 of Japan, at least between 35° and 40° N. Lat. in which the plants 

 were collected, was not in the least warmer than now. This \vould 

 naturally lead us to assume that a difference in climate had 

 already at that time existed between Europe and Japan, but that 

 this difference was not so marked as in later epochs. And I think 

 this is quite in accordance with the already known fact that the 

 further back we go into the past, the more uniform the climate 

 becomes throughout the world. 



About the Pre-Miocene Tertiary fossils of Japan we do not 

 yet know much. And the few that I myself have lately described^-* 

 are not enough to enable us to dra^v any conclusion as to the 

 climate of those times. 



The phenomena of Nature which have been already set forth 

 as the probable causes of the climatic changes of the past, and 

 especially of the ice-age, are partly astronomical and partly physical. 

 Among the former we may mention the change in the eccentricity 

 of the earth's orbit or in the obliquity of the ecliptic, the preces- 

 sion of the equinoxes, the displacement of the poles and the 

 formation of the smaller planets. Among the latter we may count 



1) Zur fossilen Flora Japans, 1888. 



•J) Some Tertiary Fossils from the Miike Coal-fielJ; 1911. 



