by the Crown; and how
strong was the architectural influence of towns upon one another up
and down the water, as also how the place names upon the banks are
everywhere drawn from the river; but before dealing with these it is
best to establish the main portions into which the Thames falls and to
see what would naturally be their limits.

It may be said, generally, that every river which is tidal, and whose
stream is so slow as to be easily navigable in either direction,
divides itself naturally, when one is regarding it as a means of
communication, into three main divisions.

There will first of all be the tidal portion which the tide usually
scours into an estuary. As a general rule, this portion is not
considerably inhabited in the early periods of history, for it is not
until a large international commerce arises that vessels have much
occasion to stop as they pass up and down the maritime part of the
stream; and even so, settlements upon its banks must come
comparatively late in the development of the history of the river,
because a landing upon such flooded banks is not easily to be
effected.

This is true of the Dutch marshes at the mouths of the Rhine, whose
civilisation (one exclusively due to the energy of man) came centuries
after the establishment of the great Roman towns of the Rhine; it is
true of the estuary of the Seine, whose principal harbour of Havre is
almost modern, and whose difficulties are still formidable for
ocean-going craft; and it is true of the Thames.

The estuary of the Thames plays little or no part in the very early
history of England. Invaders, when they landed, landed on the
sea-coast at the very mouth, or appear to have sailed right up into
the heart of the country.

It is, nevertheless, true that the last few miles of tidal water, in
Western Europe at least, are not to be included in this first division
of a great river.

The swish of the tide continues up beyond the broad estuary, the
sand-banks, and the marshes, and there are reaches more or less long
(rather less than twenty miles perhaps originally in the case of the
Thames, rather more perhaps originally in the case of the lower Seine)
which for the purposes of habitation are inland reaches. They have the
advantage of a current moving in either direction twice a day and yet
not the disadvantage of greatly varying levels of water. Thus one may
say of the Seine in the old days that from about Caudebec to Point de
L'Arche