sts were securely
stepped and could not lower from proceeding farther up stream, and
would thereupon become the boundary of the seaport of the Thames. Such
a bridge would, again, concentrate upon itself the traffic of all that
important and formerly wealthy part of the island which bulges out to
the east between the estuary of the Thames and the Wash, and which
must necessarily have desired communication both with the still
wealthier southern portion and with the Continent. But, more important
than this, London Bridge also concentrated upon itself all the
up-country traffic in men and in goods which came in by the natural
gate of the country at the Straits of Dover, except that small portion
which happened to be proceeding to the south-west of England: and this
exception to the early commerce of England was the smaller from the
comparative ease with which the Channel could be crossed between
Brittany and Cornwall.

Finally, the Bridge, as it formed the limit for sea-going vessels,
formed also if not the limit at least a convenient terminus for craft
coming from inland down the stream. It would form the place of
transhipment between the sea-going and the inland trade.

Everything then conspired to make this first crossing of the Thames
the chief commercial point in Britain; and, since we are considering
in particular the history of the river, it must be noted that these
conditions also made of London Bridge what we have remarked it to be,
the chief division in the whole course of the stream. This character
it still maintains, and the life of the river from the bridge to the
Nore is a totally different thing, with a different literature and a
different accompanying art, from the life of the river above bridges.

We have seen that the river when it is regarded as an avenue of access
to men for commerce or for travel is, especially in early times, and
with boats of light draught, of one piece from Lechlade to London
Bridge. There was in this section always sufficient water even in a
dry summer to float some sort of a boat. But the river, regarded as a
barrier or obstacle for human beings in their movement up and down
Britain, did not form one such united section. On the contrary, it
divided itself, as all such rivers do, into two very clearly defined
parts: there was that upper part which could be crossed at frequent
intervals by an army, that lower part in which fords are rare.

In most rivers one has nothing more to d