s defects, has greater advantages than any other that
has been yet proposed.

I. PRE-GLACIAL DEPOSITS.--The chief pre-glacial deposit of Britain
is found on the Norfolk coast, reposing upon the Newer Pliocene
(Norwich Crag), and consists of an ancient land-surface which
is known as the "Cromer Forest-bed."

This consists of an ancient soil, having embedded in it the stumps
of many trees, still in an erect position, with remains of living
plants, and the bones of recent and extinct quadrupeds. It is
overlaid by fresh-water and marine beds, all the shells of which
belong to existing species, and it is finally surmounted by true
"glacial drift." While all the shells and plants of the Cromer
Forest-bed and its associated strata belong to existing species,
the Mammals are partly living, partly extinct. Thus we find the
existing Wolf (_Canis lupus_), Red Deer (_Cervus elaphus_), Roebuck
(_Cervus capreolus_), Mole (_Talpa Europtoea_), and Beaver (_Castor
fiber_), living in western England side by side with the
_Hippopotamus major, Elephas antiquus, Elephas meridionalis,
Rhinoceros Etruscus_, and _R. Megarhinus_ of the Pliocene period,
which are not only extinct, but imply an at any rate moderately
warm climate. Besides the above, the Forest-bed has yielded the
remains of several extinct species of Deer, of the great extinct
Beaver (_Trogontherium Cuvieri_), of the Caledonian Bull or "Urus"
(_Bos primigenius_), and of a Horse (_Equus fossilis_), little
if at all distinguishable from the existing form.

The so-called "Bridlington Crag" of Yorkshire, and the "Chillesford
Beds" of Suffolk, are probably to be regarded as also belonging
to this period; though many of the shells which they contain
are of an Arctic character, and would indicate that they were
deposited in the commencement of the Glacial period itself. Owing,
however, to the fact that a few of the shells of these deposits
are not known to occur in a living condition, these, and some
other similar accumulations, are sometimes considered as referable
to the Pliocene period.

II. GLACIAL DEPOSITS.--Under this head is included a great series
of deposits which are widely spread over both Europe and America,
and which were formed at a time when the climate of these countries
was very much colder than it is at present, and approached more
or less closely to what we see at the present day in the Arctic
regions. These deposits are known by the general name of the
_Glacia