434 Climate of the Glacial Period. (October, 
Post Pliocene period afforded no geological evidence of a 
warmer condition of climate in Europe than now prevails, it 
would be so far a presumptive evidence against the assump- 
tion that the glacial epoch resulted from cosmical causes.” 
“Tf it should actually turn out that there is no such thing 
as a warm and equable condition of climate somewhere 
about the time of an ice period, then the whole theory 
would have to be given up, because a warm period according 
to theory is just as necessary a result of an increase of 
eccentricity as a cold period.’’* 
Now not only would the periods of great cold alternate in 
each hemisphere with periods of ‘‘ perpetual summer,” ac- 
cording to this theory, but as the ellipticity of the orbit 
approached its greatest eccentricity, warm or genial climates 
would alternate with colder ones, the extremes becoming 
more and more marked as the time of greatest eccentricity 
was neared. We ought therefore to find before the Glacial 
period evidence of great changes of climate, alternations of 
warm and cold periods, in the successive faunas, of which 
we have the records preserved in the Tertiary rocks. Instead 
of this, there are proofs of the gradual and continual 
decrease of temperature in Europe from the earliest Tertiary 
times. According to Lyell, ‘‘as we ascend in the series, the 
shells of the successive groups of strata—provincially called 
‘crag’ in Norfolk and Suffolk—are seen to consist less and 
less of southern species, whilst the number of northern 
forms is always augmenting, until in the uppermost or 
newer groups, in which almost all the shells are of living 
species, the fauna is very arctic in character, and that even 
in the 52nd and 54th degrees of north latitude.”+ And if 
we go back to earlier Tertiary times than the Crag period, we 
find all the faunas—back to the very commencement of the 
Tertiary formations—evidencing warmer and warmer climatic 
conditions as we recede from the Glacial period. Nor is this 
evidence confined to the faunas; it is perhapseven better illus- 
trated if we trace the successive floras from the Eocene up- 
wards to the Glacial period. Commencing with the Lower 
Eocene we find in the London clay the fruits of numerous 
palms, belonging to genera only now found in the tropics, 
accompanied bythe custard apple, gourds, and melons. These 
are followed intime by the Bournemouth beds, with subtropical 
Proteaceze, numerous fig-trees, the cinnamon, and many 
other plants and trees, reminding the botanist of parts of 
* Philosophical Magazine, vol. xxxvi., page 380. 
+ Principles of Geology, p. 199. 
