But the main reason is, that the silt brought down by the fen rivers
cannot, like that of the Forth and its neighbouring streams, get safe
away to sea. From Flamborough Head, in Yorkshire, all down the
Lincolnshire coast, the land is falling, falling for ever into the
waves; and swept southward by tide and current, the debris turns into
the Wash between Lincolnshire and Norfolk, there to repose, as in a
quiet haven.

Hence that vast labyrinth of banks between Lynn and Wisbeach, of mud
inside, brought down by the fen rivers; but outside (contrary to the
usual rule) of shifting sand, which has come inward from the sea, and
prevents the mud's escape--banks parted by narrow gullies, the
delight of the gunner with his punt, haunted by million wild-fowl in
winter, and in summer hazy steaming flats, beyond which the trees of
Lincolnshire loom up, raised by refraction far above the horizon,
while the masts and sails of distant vessels quiver, fantastically
distorted and lengthened, sometimes even inverted, by a refraction
like that which plays such tricks with ships and coasts in the Arctic
seas. Along the top of the mud banks lounge the long black rows of
seals, undistinguishable from their reflection in the still water
below; distorted too, and magnified to the size of elephants. Long
lines of sea-pies wing their way along at regular tide-hours, from or
to the ocean. Now and then a skein of geese paddle hastily out of
sight round a mud-cape; or a brown robber gull (generally
Richardson's Skua) raises a tumult of screams, by making a raid upon
a party of honest white gulls, to frighten them into vomiting up
their prey for his benefit; or a single cormorant flaps along, close
to the water, towards his fishing ground. Even the fish are shy of
haunting a bottom which shifts with every storm; and innumerable