climate had changed to a tropical one; and the plants and animals of
the upper part of the London clay had begun to resemble rather those
of the mouths of the African slave-rivers.

Extraordinary as this is, it is certainly true.

We know that the country near the mouth of the Thames, and probably
the land round us here, was low rich soil, some half under water,
some overflowed by rivers; some by fresh or brackish pools. We know
all this; for we find the shells which belong to a shallow sea,
mixed with fresh-water ones. We know, too, that the climate of this
rich lowland was a tropical one. We know that the neighbourhood of
the Isle of Sheppey, at the mouth of the Thames, was covered with
rich tropic vegetation; with screw pines and acacias, canes and
gourds, tenanted by opossums, bats, and vultures: that huge snakes
twined themselves along the ground, tortoises dived in the pools,
and crocodiles basked on the muds, while the neighbouring seas
swarmed with sharks as huge and terrible as those of a West Indian
shore.

It is all very wonderful, ladies and gentlemen: but be it is: and
all we can say is, with the Mussulman--"God is great."

And then--when, none knows but God--there came a time in which some
convulsion of nature changed the course of the sea currents, and
probably destroyed a vast tract of land between England and France,
and probably also, that sunken island of Atlantis of which old Plato
dreamed--the vast tract which connected for ages Ireland, Cornwall,
Brittany, and Portugal. That convulsion covered up the rich clays
with those barren sands and gravels, which now rise in flat and