but had we documents to hand (which, of course, we have not) it might
be possible to show that exceptional tracts, such as the isolated Hill
of Witham (which is much more influenced by Oxford than by Abingdon),
was treated as the land of Oxfordshire men in early times, or was
perhaps a territory in dispute; and something of the same sort may
have existed in the connection of Caversham with Reading.

In this old age of our civilisation the exactitude of the boundary
which the Thames establishes is apparent in various survivals. Islands
now joined to the one bank and indistinguishable from the rest of the
shore are still annexed to the farther shore. Such a patch is to be
found at Streatley, geographically in Berkshire, legally in Oxford;
there is another opposite Staines, which Middlesex claims from Surrey.
In all, half-a-dozen or more such anomalous frontiers mark the course
of the old river. One arrested in process of formation may be seen at
Pentonhook.

A boundary--that is, an obstacle to travel--has this further feature,
that the point at which it is crossed--that is, the point at which the
obstacle is surmounted--is certain to become a point of strategic and
often of commercial importance. So it is with the passes over
mountains and with the narrows of the sea, and so it is with fords and
bridges over rivers. So it is with the Thames.

The energies both of travel and of war are driven towards and confined
in such spots. Fortresses arise and towns which they may defend.
Depots of goods are formed, the coining and the change of money are
established, secure meeting places for speculation are founded.

Such passages over the Thames were of two sorts: there are first the