triumph and half a retreat, they went back to the eastern coast of the
island, where they found secure places of refuge to receive them.

In the course of the subsequent campaigns, a party of the Danes came
up the River Thames with a fleet of their vessels, and an account is
given by some of the ancient historians of a measure which Alfred
resorted to to entrap them, which would seem to be scarcely credible.
The account is, that he _altered the course of the river_ by digging
new channels for it, so as to leave the vessels all aground, when, of
course, they became helpless, and fell an easy prey to the attacks of
their enemies. This is, at least, a very improbable statement, for a
river like the Thames occupies always the lowest channel of the land
through which it passes to the sea. Besides, such a river, in order
that it should be possible for vessels to ascend it from the ocean,
must have the surface of its water very near the level of the surface
of the ocean. There can, therefore, be no place to which such waters
could be drawn off, unless into a valley below the level of the sea.
All such valleys, whenever they exist in the interior of a country,
necessarily get filled with water from brooks and rains, and so become
lakes or inland seas. It is probable, therefore, that it was some
other operation which Alfred performed to imprison the hostile vessels
in the river, more possible in its own nature than the drawing off of
the waters of the Thames from their ancient bed.

Year after year passed on, and, though neither the Saxons nor the
Danes gained any very permanent and decisive victories, the invaders
were gradually losing ground, being driven from one intrenchment and
one stronghold to another, until, at last, their only places of refuge
were their ships, and the harbors along the margin of the sea. Alfred
followed on and occupied the country as fast as the enemy was driven