he past distribution of the species was different
formerly to what it is now, not necessarily because the climate
has changed, but because of the alteration of other conditions
essential to the life of the species or conducing to its extension.

Still, we are in many cases able to draw completely reliable
conclusions as to the climate of a given geological period, by
an examination of the fossils belonging to that period. Among
the more striking examples of how the past climate of a region
may be deduced from the study of the organic remains contained in
its rocks, the following may be mentioned: It has been shown that
in Eocene times, or at the commencement of the Tertiary period,
the climate of what is now Western Europe was of a tropical or
sub-tropical character. Thus the Eocene beds are found to contain
the remains of shells such as now inhabit tropical seas, as, for
example, Cowries and Volutes; and with these are the fruits of
palms, and the remains of other tropical plants. It has been
shown, again, that in Miocene times, or about the middle of the
Tertiary period, Central Europe was peopled with a luxuriant
flora resembling that of the warmer parts of the United States,
and leading to the conclusion that the mean annual temperature
must have been at least 30 deg. hotter than it is at present. It has
been shown that, at the same time, Greenland, now buried beneath
a vast ice-shroud, was warm enough to support a large number of
trees, shrubs, and other plants, such as inhabit temperate regions
of the globe. Lastly, it has been shown upon physical as well as
palaeontological evidence, that the greater part of the North
Temperate Zone, at a comparatively recent geological period, has
been visited with all the rigours of an Arctic climate, resembling
that of Greenland at the present day. This is indicated by the
occurrence of Arctic shells in the superficial deposits of this
period, whilst the Musk-ox and the Reindeer roamed far south of
their present limits.

Lastly, it was from the study of fossils that geologists learnt
originally to comprehend a fact which may be regarded as of cardinal
importance in all modern geological theories and
speculations--namely, that the crust of the earth is liable to
local elevations and subsidences. For long after the remains of
shells and other marine animals were for the first time observed
in the solid rocks forming the dry land, and at great heights
above the sea-level, att