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Rob and list members, There are a few balance bob pits near where I work in North Queensland - one has a remnant wall of rock between it and the shaft and is an elongated rectangular shape with no narrowing towards the shaft (and soft friable ground conditions). The other two open directly into the mouth of the shaft with no narrowing oir even a dividing 'wall' - again in pretty crumbly ground conditions. These last two are lined with mortared granite stone work and even though they're wide open, are arguably a lot more stable than the original weathered rock they have replaced. Regards Ian Hodkinson ----- Original Message ----- From: "Robert Waterhouse" <[log in to unmask]> To: <[log in to unmask]> Sent: Tuesday, August 19, 2008 11:15 PM Subject: Balance bob pits at shaft throats > Dear List, > > > > I've recently seen two mid-C19 mortared stone angle/balance bob chambers > in > East Cornwall and West Devon, which are immediately alongside shafts, > whose > sides curve inwards immediately adjoining the shaft. This narrows the > chamber considerably to a width of about 2-3ft, from a total chamber width > of about 8ft. > > > > Does anyone know why this was done? Someone suggested that it might make > such a pit more stable where it adjoins the shaft, but as I haven't seen > these anywhere else, I'm not sure. > > > > Robert Waterhouse > > Morwellham Quay Archaeologist >