in Huel Cock, in the parish of Saint Just, and is at the present time, in two mines in the same parish, Botallack and Little Bounds.
For keeping the workings from being inundated, each mine is furnished with a chain of pumps, extending from the bottom to the adit level, worked by a single pump-rod, each pump receiving the water brought up by the one immediately below it. All the water of the lowest level finds its way into the bottom of the mine, or sump; the water from the upper levels is received into cisterns placed in different parts of the shaft, at the termination of each tier of pumps, from whence it is drawn to the adit, through which it flows outwards to the surface of the earth. The quantity of water discharged by the pumps, by many of the Cornish mines, is very considerable: thus, in 1819, Huel Abraham, 1440 feet in depth, discharged about 2,092,320 gallons every twenty-four hours; Dolcoath, of nearly the same depth, 535,173 gallons in the same time; and Huel Vor, 950 feet deep, 1,692,660 gallons.[1]
Temperature.─It results from the experience of all those who have practically investigated the subject, that the temperature of the air, earth and water of mines, at a certain depth under the surface, is very considerably greater than that of the mean of the climate of the district. It has also been universally found that the temperature increases with the depth. Both these facts I have myself ascertained, by many trials, in the mines of Cornwall, beyond the
- ↑ Memoir on the Temperature of Mines, in the second vol. of the Transactions of the Royal Geological Society of Cornwall. By John Forbes, M. D.
