Wales, Scotland, and Cornwall, forming a small
archipelago or group of rocky islands separated at some distance by a
wide passage from the nucleus of the young European continent. But by
the Wealden period, the English Channel and the Eastern half of England
had been considerably elevated above the level of the sea. Great rivers
and lakes existed in this new continental region, much like those which
now exist in Sweden, Northern Russia, and Canada; and the deposits of
sand or mud formed at their bottoms or in their estuaries compose the
chief part of the Wealden formation in England. Without going fully
into this question (somewhat complicated by frequent changes of level),
it will suffice for our present purpose to say that the Wealden
consists, in the main, of two great divisions, which form, so to speak,
the floor, or lowest story, of the Sussex formations. The first or
bottom division is chiefly composed of a rather soft and friable
sandstone, which runs through the whole Forest Ridges, and crops out in
the grey cliffs of Hastings and Fairlight. The second or upper division
is chiefly composed of a thick greasy clay, which forms the soil in the
greater part of the Weald, and glides unobtrusively under the sea in
the flat shore on either side of Hastings, giving rise to the lowlands
of Pevensey Bay and the Romney Marshes. Why the sandstone, which is
really the bottom layer, should appear higher than the clay in these
places, we shall see a little later.

After the deposition of the gritty or muddy Wealden beds in the lake
and _embouchure_ of the old continental river, there came a second
period of considerable depression, during which the whole of
south-eastern England was once more covered by a shallow sea. This sea
ran, like an early northern Mediterranean, right across the face of
Central Europe; and on its bottom was deposited the soft ooze of
globigerina shells and siliceous sponge skeletons which has now
hardened into chalk and flint. A great cretaceous sheet thus overlay
the Wealden beds and the whole face of Sussex to a depth of at least
600 feet; and if it had not been afterwards worn off in places, as the
nursery rhyme says of old Pillicock, it would be there still. I need
hardly say that the chalk is yet _en evidence_ along the whole range of
South Downs, and forms the tall white cliffs between Brighton and
Beachy Head.

Finally, during the Tertiary period, another layer of London clay and
other soft de