southern
hemispheres has generally led to great diversity of climate in the Arctic
and Antarctic regions. The form and arrangement of the continents is shown
to be such as to favour the transfer of warm oceanic currents to the north
far in excess of those which move towards the south, and whenever these
currents had free passage _through_ the northern land-masses to the polar
area, a mild climate must have prevailed over the whole northern
hemisphere. It is only in very recent times that the great northern
continents have become so completely consolidated as they now are, thus
shutting out the warm water from their interiors, and rendering possible a
wide-spread and intense glacial epoch. But this great climatal change was
actually brought about by the high excentricity which occurred about
200,000 years ago; and it is doubtful if a similar glaciation in equally
low latitudes could be produced by means of any such geographical
combinations as actually occur, without the concurrence of a high
excentricity.

A survey of the present condition of the earth supports this view, for
though we have enormous mountain ranges in every latitude, there is no
glaciated country south of Greenland in N. Lat. 61deg. But directly we go
back a very short period, we find the superficial evidences of glaciation
to an enormous extent over three-fourths of the globe. In the Alps and
Pyrenees, in the British Isles and Scandinavia, in Spain and the Atlas, in
the Caucasus {537} and the Himalayas, in Eastern North America and west of
the Rocky Mountains, in the Andes of South Temperate America, in South
Africa, and in New Zealand, huge moraines and other unmistakable ice-marks
attest the universal descent of the snow-line for several thousand feet
below its present level. If we reject the influence of high excentricity as
the cause of this almost universal glaciation, we must postulate a general
elevation of _all_ these mountains about the same time, geologically
speaking--for the general similarity in the state of preservation of the
ice-marks and the known activity of denudation as a destroying agent,
forbid the idea that they belong to widely separated epochs. It has,
indeed, been suggested, that denudation alone has lowered these mountains
so much during the post-tertiary epoch, that they were previously of
sufficient height to account for the glaciation of all of them; but this
hardly needs refutation, for it is clear that denudation could n