w find them, and thus a considerable portion of the Alps may have
been more elevated than they are now. This would certainly lead to an
enormous accumulation of snow, which would be increased when the
excentricity reached a maximum, as already fully explained, and may then
have caused glaciers to descend into the adjacent sea, carrying those
enormous masses of rock which are buried in the Upper Miocene of the
Superga in Northern Italy. An earlier epoch of great altitude in the Alps
coinciding with the very high excentricity 2,500,000 years ago, may have
caused the local glaciation of the Middle Eocene period when the enormous
erratics of the Flysch conglomerate were deposited in the inland seas of
Northern Switzerland, the Carpathians, and the Apennines. This is quite in
harmony with the indications of an uninterrupted warm climate and rich
vegetation during the very same period in the adjacent low countries, just
as we find at the present day in New Zealand a delightful climate and a
rich vegetation of Metrosideros, {124} fuchsias and tree-ferns on the very
borders of huge glaciers, descending to within 700 feet of the sea-level.
It is not pretended that these estimates of geological time have any more
value than probable guesses; but it is certainly a curious coincidence that
two remarkable periods of high excentricity should have occurred, at such
periods and at such intervals apart, as very well accord with the
comparative remoteness of the two deposits in which undoubted signs of
ice-action have been found, and that both these are localised in the
vicinity of mountains which are known to have acquired a considerable
elevation at about the same period of time.

In the tenth edition of the _Principles of Geology_, Sir Charles Lyell,
taking the amount of change in the species of mollusca as a guide,
estimated the time elapsed since the commencement of the Miocene as
one-third that of the whole Tertiary epoch, and the latter at one-fourth
that of geological time since the Cambrian period. Professor Dana, on the
other hand, estimates the Tertiary as only one-fifteenth of the Mesozoic
and Palaeozoic combined. On the estimate above given, founded on the dates
of phases of high excentricity, we shall arrive at about four million years
for the Tertiary epoch, and sixteen million years for the time elapsed
since the Cambrian, according to Lyell, or sixty millions according to
Dana. The estimate arrived at from the rate of denu