Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/416



The lower Pentowan work lies three quarters of a mile south of the upper, and about half a mile north of the sea. The plain is more contracted here than at the upper work, and the river flows immediately west of the excavation, and nearly on a level with the upper part of it. The excavation measures from north to south about 400 feet, from east to west about 250, and is 54$$\scriptstyle \frac 12$$ feet deep. In form it resembles an amphitheatre, being cut into deep stopes (as the miners term them) by which their work is upheld. The miner's object is to come at a deposit of tin five feet thick at the bottom of the pit, and as he works forward he throws behind him the waste matter. Water is conveyed from the river by a wooden trough into an insulated mass of the lower stratum, in which the tin is washed.