n the south
of Scotland, and these are stated to be "overlain by a deposit of glacial
age, so similar to the breccia below as to be with difficulty distinguished
from it."[27]

These numerous physical indications of ice-action over a considerable area
during the same geological period, coinciding with just such a poverty of
organic remains as might be produced by a very cold climate, are very
important, and seem clearly to indicate that at this remote period
geographical conditions were such as to bring about a glacial epoch, or
perhaps only local glaciation, in our part of the world.

Boulder-beds also occur in the Carboniferous formation, both in Scotland,
on the continent of Europe, and in North America; and Professor Dawson
considers that he has detected true glacial deposits of the same age in
Nova Scotia. Boulder-beds also occur in the Silurian rocks of Scotland and
North America, and according to Professor Dawson, even in the Huronian,
older than our Cambrian. None of these indications are however so
satisfactory as those of Permian age, where we have the very kind of
evidence we looked for in vain throughout the whole of the Tertiary and
Secondary periods. Its presence in several localities in such ancient rocks
as the Permian is not only most important as indicating a glacial epoch of
some kind in Palaeozoic times, but confirms us in the validity of our
conclusion, that the _total_ absence of any such evidence throughout the
Tertiary and Secondary epochs demonstrates the absence of recurring glacial
epochs in the northern hemisphere, notwithstanding the frequent recurrence
of periods of high excentricity.

_Warm Arctic Climates in Early Secondary and Palaeozoic Times._--The
evidence we have already adduced of the mild climates prevailing in the
Arctic regions throughout the Miocene, Eocene, and Cretaceous periods is
supplemented by a considerable body of facts relating to still earlier
epochs.

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In the Jurassic period, for example, we have proofs of a mild Arctic
climate, in the abundant plant-remains of East Siberia and Amurland, with
less productive deposits in Spitzbergen, and at Ando in Norway just within
the Arctic circle. But even more remarkable are the marine remains found in
many places in high northern latitudes, among which we may especially
mention the numerous ammonites and the vertebrae of huge reptiles of the
genera Ichthyosaurus and Teleosaurus found in the Jurassic deposits of the
Pa