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For the
first time, television cameras have explored the depths of the
disused chalk workings underneath the City of Norwich. Take
an online look underground.....
Watch
video: Mike Liggins goes underground (Real, G2 3'28")
Chalk
cavern beneath Norwich, pictures and words by Iain Meikle |
Norwich
is well-known for its miles of disused chalk workings - some
dating back as far as the 13th or 14th Centuries.
The mines were
sunk to exploit the rich deposits of chalk and flint that run from
NW to SE across the county.
The raw
mineral was cooked in kilns, fired originally by charcoal, then
coal and coke. In a continuous process, new chalk and fuel was
added to the top of the kiln in layers. The
end result - lime, was removed from the bottom.
Kilns would
often burn for up to a year. After cooling, the lime was mixed
with animal hair as a binding agent to form mortar for construction.
Click here to read reporter Mike Liggins' description of his
journey beneath the city
Click
here to read about Mike's visit to a sewerage tunnel and a Victorian
reservoir
See
video of the tunnel and reservoir (Real,
G2, 3'29)
Lime was used
elsewhere too. It
was spread extensively on farmland, both to neutralise acidity,
and to improve the texture of the soil. As rain fell on limed ground,
the solution helped draw together clay particles into lumps.
As a result
the earth drained much more freely.
A third use
for the material was to produce whitewash. The lime was simply added
to water, mixed and allowed to settle before being painted on to
buildings.
Lime from Norwich
produced a brisk trade to London with wherries carrying the mineral
down the River Yare to Great Yarmouth.
City engineer Gary Thompson and the 91热爆's Mike Liggins
in the workings.
The workings
are only opened every two years or so to check their condition.
As long the
chalk does not dry out too much, the tunnels and galleries remain
remarkably stable.
In nearly all
the well-known cases of collapse, burst water mains or leaking drains
have eroded soil. The
resulting cavity has then caved in.
More
underground material
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