was from very ancient times a fort, or stationary camp (L. _castra_),
against the wild Welsh.

[Illustration: EARLY BRITISH POTTERY.]

Let us consider this question as regards London. Look at the map called
'Roman London' (p. 15). You will there see flowing into the river Thames
two little streams, one called Walbrook, and the other called the Fleet
River. You will see a steep slope, or cliff, indicated along the river
side. Anciently, before any buildings stood along the bank, this cliff,
about 30 feet high, rose over an immense marsh which covered all the
ground on the south, the east, and the west. The cliff receded from the
river on the east and on the west at this point: on either side of the
Walbrook it rose out of the marsh at the very edge of the river at high
tide. There was thus a double hill, one on the east with the Walbrook on
one side of it, the Thames on a second side, and a marsh on a third
side, and the Fleet River on the west. It was thus bounded on east,
south, and west, by streams. On the north was a wild moor (hence the
name Moorfields) and beyond the moor stretched away northwards a vast
forest, afterwards called the Middlesex forest. This forest covered,
indeed, the greater part of the island, save where marshes and stagnant
lakes lay extended, the haunt of countless wild birds. You may see
portions and fragments of this forest even now; some of it lies in Ken
Wood, Hampstead; some in the last bit left of Hainault Forest; some at
Epping.

The river Thames ran through this marsh. It was then much broader than
at present, because there were no banks or quays to keep it within
limits: at high tide it overflowed the whole of the marsh and lay in an
immense lake, bounded on the north by this low cliff of clay, and on the
south by the rising ground of what we now call the Surrey Hills, which
begin between Kennington and Clapham, as is shown by the name of Clapham
Rise. In this marsh were a few low islets, always above water save at
very high tides. The memory of these islands is preserved in the names
ending with _ea_ or _ey_, as Chelsea, Battersea, Bermondsey. And
Westminster Abbey was built upon the Isle of Thorns or Thorney. The
marsh, south of the river, remained a marsh, undrained and neglected for
many centuries. Almost within the memory of living men Southwark
contained stagnant ponds, while Bermondsey is still flooded when the
tide is higher than is customary.

2. THE FOUNDATION OF LO