310 J. Croll—Arctie Interglacial Periods. 
the climate again began to grow mild and equable, it would re- 
trace its steps northward. There is, however, little doubt that 
during the severity of a glacial period, and when necessarily 
confined to a more limited area, its numbers would be greatly 
diminished. There is every reason for believing that the Mam- 
moth outlived all that succession of cold and warm periods 
known as the Glacial epoch proper, and did not finally disappear 
till recent post-glacial times. 
It was probably about the commencement of a cold period, 
and before the Mammoth had retreated from Northern Siberia, 
that those individuals perished whose carcasses have been found 
frozen in the cliffs. The way in which they probably perished 
and became imbedded in the frozen ice and mud, has, I think, 
been ingeniously shown by Dr. Rae.* 
It is true that more recent Arctic voyagers have come 1 
the conclusion that these trees must have been drifted dow? 
the river from the south. There ean be little doubt that the 
greater part of the wood found there, as in Siberia, is drift- 
Ww in Siberi 
of wood ?—a “Noashina” and a “ Adamshina,” a kind which 
was drifted and another kind which grew on the spot. This 18 
ned. 
That so little has as yet been done in the way of searching 
for such evidence of interglacial periods, is, doubtless, 7 
* Phil. Mag. for July, 1874, p. 60. 
