 |
 |
The "piece of string" in question is Devon Great Consols. In a moment of idle speculation I was wondering how close to the limit the two 40' x 12' wheels which were pumping Wheal Anna Maria and Wheal Josiah (max depth circa 150 fathoms) were. I was also wondering what would have happened if tin had been discovered below the copper and the mine went deep, say 300 fathoms? Would the mine have persevered with water power for pumping or would they have turned to steam? Rick ----- Original Message ----- From: "Peter Claughton" <[log in to unmask]> To: <[log in to unmask]> Sent: Friday, April 04, 2003 10:19 PM Subject: Re: Pumping > >>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/ > > _____________________________________________