d by Roman
work or of a bridge, nor any record of such things.

As to the second question, the road from Bicester southward runs
straight to Dorchester. At Dorchester, as we have seen, there was no
ford, though just below it a Roman ferry has been guessed at.

There may have been a country road running down along the left or
north bank of the river to the pre-historic crossing place at Goring
and Streatley; but if there was, no trace of it remains, save perhaps
in the two place names North Stoke and South Stoke.

A barrier has yet another quality in history, and that quality is
perhaps the most important of all. In so far as it is an obstacle it
is also a means of defence.

All the great rivers of Europe prove this. They are studded with lines
of strongholds standing either right upon their banks or close by; and
various as is the character of the different great rivers in their
physical conformation, few or none have been unable to furnish sites
for fortification. For instance, the slow rivers of Northern France,
running for the most part through a flat country, were able to afford
fortresses for the Gaulish clans in their numerous islands; the origin
of Melun and Paris, for instance, was of this kind. The sharp rocks
along the Rhone became platforms for castle after castle: Beaucaire,
Tarascon, Aries, Avignon, and twenty others all of this sort.

The Thames, curiously enough, forms an exception; it is an exception
even in the list of English rivers, most of which can show a certain
number of fortifications along their banks.

In the whole course of the great river above London there are but
three examples of fortification, or at any rate of fortification
directly dependent upon the river. Of these the first, at Lechlade, is
conjectural; the second, at Windsor, came quite late in history, and
the only one which seems to have been a primeval fortified site was
Dorchester.

There were, of course, plenty of towns and castles susceptible of
defence. At one time or another every important settlement upon the
Thames was capable of resistance: Oxford was walled, Wallingford was a
fortress, Abingdon or Reading could be defended. But these were all,
so to speak, artificial. The settlement came first, and after the
settlement the necessity of guarding it from attack, and it was so
guarded, not by natural means, but by human construction. The castle
at Oxford, for instance, stood upon a mound of earth raised by human
wor