>>From what depth can a waterwheel driven set of Cornish pitwork pump from?
Rick,
The question is something akin to the question 'how long is a piece of
string' as there are some many variables to be considered.
Much depends on the amount of water the mine is making, which might be a
factor of amount of ground developed at a particular depth; add to that the
amount, and head, of water available at surface to provide the power source.
A relatively small mine in the south-west of England, like Bampfylde at
North Molton which pumped to the 112 fathom level in the third quarter of
the 19th century, could manage quite well with water power alone whilst
other, much shallower, mines were reliant on steam power. Whereas, I'm sure
the Lady Isabella wheel, at Foxdale on the Isle of Man, put in a sterling
performance in terms of the quantity of water it lifted.
One limitation on the typical 'Cornish' arrangement, of a suction lift
bottom 'bucket' lift and a series of forcing pumps feeding a rising main to
surface, was the ability of the material available to withstand the pressure
of the accumulated water. I would suggest that the materials available
through advances in iron technology in the late 18th century, when Cornish
copper mining was attaining greater working depths, made the use of forcing
pumps possible in larger, i.e. deeper, continuous lifts. Prior to the
availability of cast iron rising mains, pumping was limited by the strength
of the wooden barrels used in suction lift pumps - requiring a number of
short staged lifts, sometimes called 'shamelling' in reference to the much
earlier practice of baling water from one level to another.
As to where the mechanised forcing pump was first used as the main lifting
pump is open to debate but, given the increasing depth of Cornish mines in
the late 18th century, they are in with a chance. Mechanised, i.e. water or
steam powered, is the key because manually operated forcing pumps were used
in mid Wales and Devon for short lifts at a much earlier date.
Peter
______________________________________________
Peter Claughton, Blaenpant Morfil, Rosebush, Clynderwen,
Pembrokeshire, Wales SA66 7RE.
Tel. 01437 532578; Fax. 01437 532921; Mobile 07831 427599
University of Exeter - School of Historical, Political and Sociological Studies
(Centre for South Western Historical Studies)
E-mail: [log in to unmask]
Co-owner - mining-history e-mail discussion list.
See http://www.jiscmail.ac.uk/files/mining-history/ for details.
Mining History Pages - http://www.exeter.ac.uk/~pfclaugh/mhinf/
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