ARCTIC INTERGLACIAL PERIODS. 185 



will, however, be found discussed at great length in 

 Professor Geikie's " Prehistoric Europe " and in " The 

 Great Ice Age " (second edition). Mr. R. A. Wallace 

 considers that one of the last intercalated mild periods 

 of the Glacial Epoch seems to offer all the necessary 

 conditions for the existence of the mammoth in Siberia. 

 That the mammoth was interglacial will be further 

 evident when we consider the climatic conditions of 

 Europe at the time that it lived there. Before doing 

 so, it may be as well to glance at what evidently were 

 the main characteristics of the interglacial periods. 



Main Characteristics of Interglacial Climate. — 

 They are as follows : — 



1. Interglacial conditions neither did nor could exist 

 simultaneously on both hemispheres. They existed 

 only on one hemisphere at a time, viz., on the hemi- 

 sphere which had its winter solstice in perihelion. 



2. During interglacial periods the climate was more 

 equable than it is at present ; that is to say, the differ- 

 ence between the summer and winter temperatures 

 was much less than it is now. The summers may not 

 have been warmer or even so warm as they are at 

 present, but the temperature of the winters was much 

 above what it is at the present day. 



3. During interglacial periods the quantity of equa- 

 torial heat conveyed by ocean-currents into temperate 

 and polar regions was far in excess of what it is at 

 present. On this account a greater uniformity of 

 climate then prevailed ; that is to say, the difference of 

 climatic conditions between the sub-tropical and the 

 temperate and polar regions was less marked than at 

 present — the temperature not differing so much with 

 latitude as it now does. 



4. Mildness, or a comparative absence of high winds, 

 characterised interglacial climate. This partial exemp- 



