OSBORX. REVIEW OF THE PLEISTOCENE 241 



Moderate Estimates of Temperature. — That the advancing glaciers 

 alone do not constitute proof of very low temperatures is observed in 

 Alaska, where very heavy snowfall or precipitation causes the accumula- 

 tion of great glaciers, although the mean annual temperature of the 

 glacier region is 40°-45° F. (4.44°-7.22° C.) as compared with that of 

 northern Germany, 45°-50° F. (7.22°-10° C), i. e., from mouth of 

 Ehine S. E. along source of northward flowing rivers, e. g., Elbe, Vistula, 

 etc. Neumayr estimated that during the Ice Age there was a general 

 lowering of temperature in Europe of not more than 6° C, and held that 

 even during the glacial advances a comparatively mild climate prevailed 

 in Great Britain. Martins estimated that a lowering of temperature to 

 the extent of 4° C. would bring the glaciers of Chamonix clown to the 

 level of the plain of Geneva. Penck estimates that all other atmospheric 

 conditions remaining the same as now a fall of temperature to the extent 

 of 4° to 5°' C. would be sufficient to bring back the Glacial Epoch in 

 Europe. Perhaps the strongest proof that Europe was not refrigerated 

 during the first, second and third glacial advances is the survival of the 

 African-Asiatic fauna throughout the whole period until the fourth 

 glaciation, which was accompanied by widespread severity of climate. 



Warm and Temperate Interglacial Stages. — Similarly the early hy- 

 potheses of extremely warm or subtropical conditions, based chiefly upon 

 the northerly distribution of hippopotami and rhinoceroses, animals 

 which we now associate with tropical conditions, are not supported by the 

 study of the interglacial flora. It is quite probable that both the hippo- 

 potami and rhinoceroses of the so-called "warm fauna" were covered with 

 hair although by no means so thickly covered as the woolly rhinoceros 

 and elephant of the arctic tundras. There is evidence that in the First 

 Interglacial Stage southern England and France enjoyed somewhat 

 warmer and moister conditions of climate than the present. The Second 

 Interglacial Stage also, which is commonly distinguished as the "long 

 warm" Interglacial Stage, was of somewhat higher temperature than the 

 present. The general evidence is that both in Europe and North Amer- 

 ica, especially in the First and Second Interglacial intervals, the climate 

 in the northern hemisphere was somewhat more equable and milder than 

 at present, with a higher mean temperature, at certain intervals with 

 greater precipitation of moisture, at other intervals much more cool and 

 arid. There was perhaps more sunshine than now. 



As a result of favorable interglacial conditions arboreal vegetation 

 flourished to the far north along the Arctic ocean, and the present tundra 

 regions of Siberia and British America then supported forests which 



