our highest mountain
ranges in England, Scotland, and Ireland. But a widespread belief seems
to prevail that the presence of glaciers implies a very low temperature.
Snow and ice, however, are formed as soon as the temperature falls below
freezing point; it does not matter whether there be 1 or 20 degrees of
cold. Winters with a few degrees of frost will be just as favourable for
the growth of glaciers as winters with the most severe cold.

Let us now see what the fauna and flora, as far as we know it, tell us
of the climate of the Glacial period. At the very outset of our inquiry
we are confronted with one very serious difficulty in the problem, and
that is the supposed occurrence of inter-glacial mild phases alternating
with colder ones during the Ice Age. At first, when traces of a
temperate flora and fauna were discovered intercalated between two
layers of boulder clay, their presence was explained by the supposition
of a mild inter-glacial period. The famous Forest-bed on the east coast
of England was also pronounced to be an inter-glacial deposit, though
not coming precisely under this definition. In a few places one such bed
was found, in some two or more, and in others none at all. Professor
James Geikie discovered the evidences of no less than five of such
inter-glacial epochs (p. 612) in Europe. Lest a reader of that author's
remarkable work on the Ice Age might carry with him the idea that his
hypotheses had met with general acceptance, a few quotations from almost
equally high authorities on glacial matters will be useful. "That the
glaciers," remarks Professor Bonney (p. 245), "were liable to important
oscillations seems to be proved, but whether the evidence suffices to
establish inter-glacial epochs, in the usual sense of the words, is more
doubtful. When the snow-fields, as in the Alps, were much more
extensive than they are at present, the glaciers which radiated from
them would be more sensitive to minor climatal change. Even now they
oscillate considerably. But during a Glacial epoch, an inch, either more
or less, of precipitation might mean a considerable advance or retreat
of the ice in the lowlands." French geologists look with even less
favour on Professor Geikie's theories. Mr. Falsan (p. 212) says that he
agrees with Messrs. Favre, de Saporta, Lory, de Mortillet, Desor, de
Lapparent, Lortet, Chantre, Benoit, Fontannes, Deperet, and many other
geologists, that there was only a single Glacial perio