J. Croll—Arectic Interglacial Periods. 303 
covered with snow for nine months in the year and the tempera- 
ture is seldom much above zero Fahr. And even if they could 
havé endured the cold, they would have starved for want of 
food. Some parts of Siberia are no doubt fertile, as, for ex- 
ample, the valley of the Yenisei, described by Nordenskjéld ;* 
but there is little doubt, as Mr. Howorth remarks, that the 
larger portion of Northern Siberia, where the Mammoth and 
the Rhinoceros lived, is now a naked tundra covered with moss, 
on which no tree will grow. On such ground it is physically 
Impossible that the Mammoth and Rhinoceros could exist, for 
they cannot graze close to ground like oxen. They live on 
Ss grass and on the foliage and small branches of trees. 
vidence from Wood.—The fact that the Mammoth was most 
abundant beyond the present northern limit of wood is pretty - 
good evidence that the climatic condition of Northern Siberia 
must have been milder than now. Wood must have extended, 
m the days of the Mammoth, far beyond its present limit, 
Probably as far north as New Siberia: facts of observation sup- 
port this conclusion. 
The wood found in Northern Siberia consists of two classes 
—the one is the result of drift, the other grew on the spot. 
The natives call the former “ Noashina,” and the latter “ Adam- 
shina ;” and the division is supported by Géppert, “ who sepa- 
moth. 
In the middle of October, 1810, Hedenstrom went across the 
tundra direct to Ustiansk. “On thi 
and 80 versts from the nearest forest.” 
On the same journey Hedenstrom noticed “on the tundra, 
®qually remote from the present line of forest, among the steep 
Sandy banks of the lakes and rivers, large birch trees, com- 
plete; with bark, branches and root. At the firs glance they 
* * Nature,’ Dec. 2, 1875. + Wrangell, p. 491. 
