48 
PROCEEDINGS OE THE PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
prevalent, while even in Southern Europe the old 'mol- 
luscan fauna bespeak colder and wetter conditions 
than now obtain in those low latitudes. Thus the 
animal and plant life was quite in keeping with the 
physical conditions of that cold epoch during which 
glacier-ice covered such extensive tracts in the temperate 
latitudes of Europe. 
As evidence that those cold climatic conditions did 
not obtain persistently during the Ice Age, Dr Geikie 
then glanced at the facts in connection with the former 
presence in Europe of a fauna and flora very different 
from those which he had just described. Hippopota¬ 
mus, rhinoceros, elephant, hyaena, lion, tiger, and a great 
number of temperate species, such as deer, urus, hare, 
rabbit, &c., wandered over all Central and North-Western 
Europe; while at the same time such plants as the fig-tree, 
the laurel of the Canary Islands, the Judas-tree, and such 
like, grew spontaneously in the latitude of Paris. It is 
remarkable that the remains of these plants are found 
commingled with others which are essentially temperate 
species. Such an association of species nowhere occurs 
now in Europe; and the inference to be drawn from the 
facts was simply this: that at the time those plants were 
growing the climate of Northern Erance and of Germany 
was exempt from extremes. The summers were not so 
hot and dry, and the winters were not nearly so cold. 
Precisely the same tale is told by the land and fresh-water 
shells which accompany that remarkable flora. 
Dr Geikie then showed how the glacial deposits them¬ 
selves contained intercalated beds of sand, silt, &e., 
which had yielded more or less abundant remains both 
of the arctic-alpine and southern faunas. And he pointed 
out that the evidence led to the conclusion, that the so- 
called Glacial Period was not one long continuous period 
of cold conditions, but was interrupted several times by 
intervening periods of mild and genial conditions. In 
short, the Glacial Period consisted of an alternation of 
cold and genial epochs. 
Now, it was of the climatic and geographical changes 
which had taken place since the close of that remarkable 
alternation of strongly-contrasted climates that he was 
about to speak. 
The Post-glacial deposits were those accumulations 
which had formed after the disappearance of the great 
snow-fields and vast mers de glace ,—for the last stage of 
the so-called Glacial Period was one of intense arctic 
conditions. 
The Post-glacial and Recent deposits were typically 
represented by our peat-bogs, river and lake alluvia, and 
raised beaches. 
After describing the general structure, composition, - 
and mode of growth of peat, and pointing out that it 
was essentially a marshy accumulation,—and one which 
indicated the presence or former presence of wet and 
humid conditions,—Dr Geikie went on to describe its 
geographical distribution over Europe. From his ac¬ 
count it appeared that peat-bogs were most common, 
and attained the largest development, in Northern and 
North-Western Europe. In the South of Europe the 
peat-bogs were more local and isolated, and generally 
occurred at high elevations, as compared with the low- 
lying bogs of the North. At low levels in Southern 
Europe the bogs do not appear to be growing. 
The facts connected with the appearance of buried trees 
in and underneath the peat-bogs were next dwelt upon. 
It was shown that these occurred on at least two levels in 
many countries in North-Western Europe. At the bot¬ 
tom of the bogs, oak, hazel, ash, and other leafy trees 
were the prevailing forms, although pines now and again 
occurred; and as the trees were very often rooted in the 
underlying sub-soil, there could be no doubt that they 
actually grew in place. Above this ancient buried forest 
came a variable thickness of peat,—from two or three up 
to six, eight, or more feet,—and this peat was covered by 
a second forest-bed, which in Norway and Sweden con¬ 
sisted exclusively of pine. In Scotland and Ireland a 
second forest-bed also occurs, the trees in which consist 
principally of pine, but in lowlying districts, oaks and 
deciduous trees are also present. 
The next point of interest in the peat-bogs was their 
occasional occurrence at and below the level of the sea. 
These were the submerged peat and so-called submarine 
forests which were so commonly met with upon the low, 
flat, and shelving shores of our own islands and the oppo¬ 
site coasts of the Continent. By means of a large map, 
Dr Geikie then indicated the distribution of those sub¬ 
marine bogs and trees. These, he said, were the principal 
facts connected with the peat-bogs. 
He then went on to describe the Post-glacial and Re¬ 
cent deposits of alluvium. These occur chiefly along the 
courses of streams and rivers, or along the margins of lakes 
and estuaries. Undoubtedly they were composed of the 
sediment carried down from the interior by running water. 
The appearances presented by the old alluvia were often 
indicative of larger rivers than now flowed in our valleys. 
The mammalian remains associated with the peat-bogs 
and freshwater alluvia represent a fauna very much the 
same as that which now characterises Europe. Some of 
the animals had no doubt been locally exterminated, such 
as elk, reindeer, wolf, and beaver in Britain; while a few 
