306 J. Croll— Arctic Interglacial Periods. 
mild periods of the Glacial epoch seems to offer all the neces- 
sary 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 simul- 
taneously on both hemispheres. They existed only on one 
emisphere at a time, viz: on the hemisphere 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 difference 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. ; 
. During the interglacial periods the quantity of equatorial 
heat conveye y ocean-currents into temperate an lar 
regions was far in excess of what it is at present. On this 
account a greater uniformity of climate then prevailed: that 1s 
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, charac- 
terized interglacial climate. This partial exemption from high 
winds resulted from the fact that the difference of temperature 
between the equator and the poles, the primary cause of the 
winds, was much less than at the present day. : 
5. Another character of interglacial climate was @ higher 
large a0 
amount of warm intertropical water. In short, it was the 
presence of so much warm water from intertropical regions 
which mainly gave to the climate of the interglacial periods 
these characteristics of interglacial climate have been 
fully established by the facts of geology, but they are als% o.. ) 
