rdly a possibility of error, but
one alone is not sufficient, because it can be the effect of another
cause.

No doubt the temperature was really lower at the quaternary age and at
the epoch generally assigned to man's advent in European countries,
but the difference was not so great as some say. A lowering of four
degrees is sufficient to explain the ancient extension of the
glaciers. We can look on this figure as the maximum, for it is proved
to-day that humanity played the main _role_ in the glacial phenomena.
The beds of rivers and the alluvia are there to tell that all the
water was not in a solid state at that time, that the glaciers were
much more extended than in our days, and that the courses of the
rivers were infinitely more abundant. When this is understood we can
reasonably reduce the extension of the ancient glaciers, the lowering
of the temperature at the quaternary age, and account for the
uninterrupted life of the fauna and flora. However, we must not fall
into the opposite excess and assert, as some have done, that the
glacial period is comparatively recent, the traces of which are too
plain and fresh in some localities to assign to it an age prior to
man, and that the temperature has rather lowered itself since this
epoch. The ancient extension of the glaciers has been followed by a
corresponding growth and extension of animal life, thus proving that
the permanence of glaciers is a wise provision and absolutely
essential to man and the high orders of animals and vegetation. The
ancient extension does not prove alone that it was much colder than in
historic times, for the animals themselves are proof of this. At that
time the plains of Europe, and of France in particular, were animated
by herds of reindeer, gluttons, camels, and marmots, which one does
not find to-day except in the higher latitudes or more considerable
heights. The mammoth and rhinoceros are no exception to this, for
naturalists know they were organized to live in cold countries.

Space will not permit us to pursue this point further, or speculate on
the probable climatic conditions of the ice age; but we can carry
ourselves back a few thousand years and describe the climate of Europe
and neighboring countries of Africa and Asia. Herodotus describes the
climate of Scythia in terms which would indicate in our day the
countries of Lapland and Greenland. He shows us the country completely
frozen during eight months of the year; the Blac