shrimps are almost the only product of the shallow barren sea:
beside, all is silence and desolation, as of a world waiting to be
made.

So strong is the barrier which these sea-borne sands oppose to the
river-borne ooze, that as soon as a seabank is built--as the
projectors of the 'Victoria County' have built them--across any part
of the estuary, the mud caught by it soon 'warps' the space within
into firm and rich dry land. But that same barrier, ere the fen was
drained, backed up for ages not only the silt, but the very water of
the fens; and spread it inland into a labyrinth of shifting streams,
shallow meres, and vast peat bogs, on those impervious clays which
floor the fen. Each river contributed to the formation of those bogs
and meres, instead of draining them away; repeating on a huge scale
the process which may be seen in many a highland strath, where the
ground at the edge of the stream is firm and high; the meadows near
the hillfoot, a few hundred yards away, bogland lower than the bank
of the stream. For each flood deposits its silt upon the immediate
bank of the river, raising it year by year; till--as in the case of
the 'Levee' of the Mississippi, and probably of every one of the old
fen rivers--the stream runs at last between two natural dykes, at a
level considerably higher than that of the now swamped and
undrainable lands right and left of it.

If we add to this, a slope in the fen rivers so extraordinarily
slight, that the river at Cambridge is only thirteen and a half feet
above the mean sea level, five-and-thirty miles away, and that if the
great sea-sluice of Denver, the key of all the eastern fen, were
washed away, the tide would back up the Cam to within ten miles of
Cambridge; if we add again the rainfall upon that vast flat area,