But if the
sinking process which was going on continued a few hundred years, all
that huge mass of wood and leaf would be sunk beneath the swamp, and
covered up in mud washed down from the mountains, and sand driven in
from the sea; to form a bed many feet thick, of what would be first
peat, then lignite, and last, it may be, coal, with the stems of
killed trees standing up out of it into the new mud and sand-beds
above it, just as the Sigillariae and other stems stand up in the
coal-beds both of Britain and of Nova Scotia; while over it a fresh
forest would grow up, to suffer the same fate--if the sinking process
went on--as that which had preceded it.
That was a sight not easily to be forgotten. But we need not have
gone so far from home, at least, a few hundred years ago, to see an
exactly similar one. The fens of Norfolk and Cambridgeshire, before
the rivers were embanked, the water pumped off, the forests felled,
and the reed-beds ploughed up, were exactly in the same state. The
vast deposits of peat between Cambridge and the sea, often filled
with timber-trees, either fallen or upright as they grew, and often
mixed with beds of sand or mud, brought down in floods, were formed
in exactly the same way; and if they had remained undrained, then
that slow sinking, which geologists say is going on over the whole
area of the Fens, would have brought them gradually, but surely,
below the sea-level, to be covered up by new forests, and converted
in due time into coal.
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