as a boundary.

Its higher and hardly navigable streams are not so used. The upper
Thames and its little tributaries for some ten miles from its source
are not only indifferent to county boundaries, but run through a
territory which has been singularly indefinite in the past. For
instance, the parish of Kemble, wherein the first waters now appear,
has been counted now in Gloucester, now in Wilts. But when these ten
miles are run, just after Castle Eaton Bridge, and not quite half way
between that bridge and the old royal palace at Kempsford, the Thames
becomes the line of division between two counties, and from there to
the sea it never loses its character of a boundary.

It is a tribute to the great place of the river in history that there
is no other watercourse in England nor any other natural division of
which this is so universally true.

The reason that the Thames, like so many other European boundaries,
has come late into the process of demarcation, and the reason that its
use as a limit is more apparent in civilised than in uncivilised
times, is simply the fact that limits and boundaries themselves are
never of great exactitude save in times of comparatively high
civilisation. It is when a complex system of law and a far-reaching
power of execution are present in a country that the necessity for
precise delimitation arises. In the barbaric period of England there
was no such necessity. Doubtless the men of Berkshire and the men of
Oxfordshire felt themselves to be in general divided by the stream;
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 proce