1874.] Climate of the Glacial Period. 457 
putrefied. The ice, therefore, is as old as the close of the 
Glacial period, at which time these great quadrupeds 
flourished, and at Yakutsk has remained unmelted all that 
time. It seems impossible that it could have done so to a 
depth of 400 feet from the surface if the earth was a cooling 
globe. If, however, the heat of the crust of the earth is due 
to movements within it, we can understand that in Siberia 
it may not have been developed to the same extent as in other 
parts; for, according to the researches of Murchison, that 
country is situated on an area of great geological stability. 
According to Von Cotta, it was never below the level of the 
ocean from the close of the Permian epoch up to the Glacial 
period; and I have been able to determine that this perma- 
nence of level has continued up to the present time, and that 
the strata of the Steppes are fresh-water deposits, excepting 
those round the extreme northern extremity of the country. 
If, whilst accepting Mallet’s ably worked out theory that 
volcanoes are the result of movements of the crust of the 
earth, I am right in ascribing these movements—not with 
him to the secular cooling of the globe—but to the forces 
tending to restore the equilibrium of the earth’s figure, 
disturbed by the accretion of ice at the poles during the 
Glacial period and its subsequent liquefaction, it will add 
another to the many wonderful effects due directly and 
indirectly to the action of the sun. It was the heat of the 
sun that raised the water by vapourisation to the level at 
which it congealed near the poles; and after the earth had 
approached its normal form by the sinking of polar lands, 
it was the heat of the sun that disturbed the equilibrium 
again by melting the snow and ice and allowing it to flow 
towards the equator. Not only volcanoes but the folding 
of strata might be produced by these movements of elevation 
and depression ; but I guard myself against expressing an 
opinion whether or not the earlier and greater geological 
folds and upheavals might not be due to other causes. 
I have now brought forward a great variety of evidence, 
drawn from very different sources, that points to the probability 
of the Glacial periods of the two hemispheres having been 
contemporaneous. Of the two astronomical theories it is 
in favour of the one founded on a great increase in the ob- 
liquity of the ecliptic, for that would cause a heaping up 
of ice around the two poles at the same time. I shall now 
turn to the consideration of a most important class of facts 
only incidentally alluded to in the foregoing pages. 
We have not only to account for the cold of the Glacial 
period, but for its converse—the heat of Early Tertiary times. 
