Hello, everybody:
It's been a very interesting discussion on "bell pits", and I'm with those who
are very sceptical.
The only observation that I can make that might add to the discussion is that
they weren't even used in flint mining in Neolithic East Anglia.
Unfortunately, it is over 50 years since I visited Grime's Graves near Brandon,
Norfolk, and I can't remember how many shafts there were, or how closely spaced
they were. I think there were many, and the dates ranged back to 5,000 years ago
(if anyone gets serious on following up on this note, PLEASE check all
measurements and dates with Ancient Monuments - I was only 11).
However, my memory of the one pit that had been excavated and opened to the
public is very clear. It was indeed bell-shaped (only upside-down - the top was
the mouth of the bell - due to erosion). It was 20-30 feet deep. The actual
workings consisted of a series of narrow passages running out "radially" from
the bottom - in quotes because they bent and twisted, and at least one looped
back to the bottom of the hole. The height and width of these passages were
such that, even as an eleven-year-old, I found it quite difficult to worm my way
through the smallest. The longest passages were at most 20 feet, and this
agrees with my experience in digging exploration cross-cuts in Africa a few
years later - you start to have ventilation problems with such narrow workings
at that distance (I have made previous comments about this on the list - and
have had a correspondence with Beno Rothenberg, whose group has been excavating
somewhat similar ancient copper mines near Timna, Israel). I think it was on
this list a couple of weeks ago that someone mentioned putting a furnace at the
bottom of a shaft to create ventilation - this will work temporarily, (except of
course if you are mining coal!).
The National Trust blurb said that the ancients had worked the outcrop of the
seam of flint along the edge of the adjacent valley (I didn't see this), and had
realized that they could reach it by sinking pits away from the outcrop. They
also must have learned quite quickly that it was dangerous to try to take out
all of the seam from one pit, and that pillars were necessary, though that would
be a far too formal term for what I remember. In fact, the passages were very
narrow - much more so than I would imagine those in coal to be. This is true
in spite of the fact that the poorly-bedded, non-fissile chalk probably makes a
much more stable roof than the shale in many coal mines. At this distance in
time and space, though, I have no idea whether the passages may have been
narrower due to selective mining of only the best flint nodules.
I "believe" that I read that some of the workings connected with those in
adjacent pits, but someone would have to go to Brandon to check that out. The
upside-down bell-shape of these pits, representing 5,000 years of erosion,
probably means that no trace is left of how the mineral and the people got in
and out - in modern Africa and, it seems, at Timna, the people got in and out by
shinnying up and down the (very narrow) shafts in bare feet. In Africa we used
a builder's bucket on the end of a rope to haul the dirt out. In view of the
"lads and lassies" in E. Lancashire moonlighting on their own, there is some
evidence (mainly from the sizes of the smallest workings) of young children
doing the mining in ancient (and not so ancient) mines - some Sicilians will
still speak to you disapprovingly of the use of 6-year-old boys a hundred years
ago in the British-owned Sulphur mines.
Incidentally, exploration shafts in Zambia that were 30-40 years old still had
vertical sides: it thus may take quite a while for the bell shape to develope
under some circumstances. However, if there is a collapse at depth, forming a
"right-way up" bell, then this will progress rapidly (one or two years) to the
surface in the weathered material in which our pits were dug. Thus, as Clive
has suggested, extensive areas of "bell-pit"-type subsidence, especially if
relatively young (one or two hundred years, rather than thousands) may mean that
miners were pushing their luck, even if they were using drifts and leaving
pillars.
Also, large-scale room-and-pillar mining of relatively shallow (a few hundred
feet) anthracite in the Susquehanna area of Pennsylvania is now forming
rectilinear patterns of subsidence on the surface as the rooms beneath collapse.
This is distinct from the collapse of an old shaft to form a conical depression,
but I'm not sure that one could tell the difference from the surface (i.e.
without trenching to see a cross-section) after a few rainy seasons have washed
surrounding debris into the depressions. The mining was less than 100 years
ago, and under the control of mining engineers, so I'm sure these rooms were
designed to begin collapsing soon after production finished, and it has taken a
few decades for it to propagate up to the surface. The pattern at the surface
might resemble what some people have described on the list, with the exception
that the individual areas of collapse might be bigger.
Sorry most of this has nothing to do with coal, but I think it does put some
perspective on small-scale (or "primitive", if you will) mining methods, and the
low likelihood that anything like a true "bell-pit" was ever in extensive use.
John
John Berry Assocs - Remote Sensing Services
5000 Beverly Hills Drive, AUSTIN, TX 78731
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----- Original Message -----
From: Automatic digest processor <[log in to unmask]>
To: Recipients of mining-history digests <[log in to unmask]>
Sent: Saturday, January 11, 2003 6:05 PM
Subject: mining-history Digest - 10 Jan 2003 to 11 Jan 2003 (#2003-10)
> There are 7 messages totalling 401 lines in this issue.
>
> Topics of the day:
>
> 1. Bell Pits (4)
> 2. Fairley, W - Mining Engineer
> 3. Bell pits
> 4. List admin - not for discussion
>
> ----------------------------------------------------------------------
>
> Date: Sat, 11 Jan 2003 07:10:19 EST
> From: Clive Seal <[log in to unmask]>
> Subject: Re: Bell Pits
>
> I have questioned the bell pit theory for some time, particularly since I
> studied the Brampton Coalfield in East Cumberland. I was fortunate enough to
> dig up quite a few early 18th cent engineers reports on these pits which
> helped explain many things, as they usually included (rudimentary) plans.
>
> ********************************************************************
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