Depth of Frost in Cikcum polar Regions 35 



tures : Arctic Vegetation," summarizes as follows : " In attempting 

 to picture to ourselves the conditions which obtained during the Gla- 

 cial period, it is frequently forgotten that a very low temperature is 

 not of that importance which it is often considered to be in bringing 

 about an Ice Age. 



"Wallace"' and many others have laid stress on the necessity for 

 a concurrence of several conditions in order to render possible an 

 abnormal extension of snow and ice. 



" Whitney "^ in his comprehensive monograph on the climatic 

 changes of later geological times, has argued for the possibility of the 

 former extension of snow and ice without any violent changes in 

 climatic conditions. 



" After considering the question at length he remarks, ' The 

 entire body of facts presented brings out most clearly the true con- 

 dition of things, namely, that the Glacial epoch was a local phe- 

 nomenon, during the occurrence of which much the larger of the 

 land masses of the Globe remained climatologically entirely un- 

 affected.' As illustrating the possibility of glaciers existing in 

 places whose mean temperature differ by several degrees we may 

 notice some observations given by Woeikof."" He shows clearly 

 how other conditions than merely a low temperature are essential to 

 ice extension. Comparing the temperature taken at the lower ends 

 of glaciers in East Siberia and the west of New Zealand, there 

 is found to be a difference of more than 20° ; at Irkutsk in East 

 Siberia the temperature recorded being — 10.2°, in New Zealand 

 10°. Glaciers occur in the latitude of Nice and Florence extend- 

 ing to 212 meters above the sea level having at their lower ends 

 a mean annual temperature corresponding to that of Vienna and 

 Brussels, and warmer than that of Geneva and Odessa, with a 

 winter temperature higher than that of Florence. 



" There is the often-quoted case of the Tasman glacier descending 

 towards the West coast of New Zealand ; here the terminal face of 

 the ice is 705 feet above sea level, and is ' hidden by a grove of Pines, 

 Ratas. Beeches, and arborescent Ferns in the foreground.' 



" All these facts show us that the idea of the coexistence in the 

 same region of vegetation — in some cases of an almost tropical 

 facies — and ice fields is not so inconceivable as one might suppose. 



" Island Life. 



^' The climatic changes of later geological times. Mem. Mus. Harvard 

 Coll., Vol. VII, No. II, 18S2, p. 387- 



^* Gletscher und Eiszeiten in ihrem Verhaltnisse zum Klima. Zeit. Gesell. 

 fiir Erdknnde zn Berlin, Vol. XVI, 1881, p. 217. 



