82 OEIGIN OF LIFE IN AMEEICA 



Dr. Tclherski's * expedition to the New Siberian Islands were 

 published by the Academy of Sciences in St. Petersburg ; and 

 it is of interest to note that he arrived at conclusions similar 

 to those of Sir Henry Howorth. He contended that the causes 

 which produced glaciation in Europe acted in quite a "different 

 manner on the conditions of life in northern Siberia, where 

 the climate remained as a direct continuation of that pre- 

 vailing in Tertiary times, so that this country had a higher 

 teimperature during the Pleistocene Period than obtains at 

 present. 



He looks upon Siberia as a country in which the processes 

 of general refrigeration of the northern hemisphere and the 

 deterioration of the conditions of existence for plant and 

 animal life during the post-Tertiary Period took a regular 

 and steady course. 



Baron von Toll concurs with Tcherski and other writers in 

 their opinion that the large mammals whose carcases and 

 skeletons are now unearthed in the extreme north of Siberia 

 really lived there, but he urges that they did not arrive there 

 until after the Glacial Epoch. Underground ice, as in some 

 parts of Alaska, is extensively met with in northern Siberia 

 and in the New Siberian Islands. Its occurrence, according 

 to Baron von Toll, is due partly to a recent origin in crevices 

 and lateral infiltration, partly to a former glaciation of Siberia, 

 the ice having been preserved as " relict ice " from the Glacial 

 Epoch. Being a follower of those who connect that period 

 with a universal lowering of temperature, his contention is 

 that northern Siberia enjoyed a milder climate in post-Glacial 

 times, and that the mammoth, horse, rhinoceros and other 

 mammals were thereby induced to visit the shores of the Arctic 

 Ocean and the New Siberian Islands, which, according to 

 Baron von Toll,t were then connected with Siberia and arctic 

 America. 



The mammoth and many other animals, as I have indi- 

 cated, invaded America from Asia. Consequently, if we can 

 determine whether a land connection existed between the 

 two continents, how long it lasted, and what species made use 

 of it in their travels, some valuable data may be obtained as a 



* Tcherski, J. D., "Das Janaland," p. 469. 



t Toll, Eduard von, " Die fossilen Eislager," pp. 80—85. 



