any other given weight of coal consumed in working a
steam engine; since the quantity of water that the engine
will raise to a given height, or the number of quarters of
corn that it will grind, or, in short, the amount of any other
description of work that it will do, is proportionate to that
duty. As the principal working of mineral veins can only
be continued by descending deeper every year, the difficulty
of extracting metals is continually on the increase,
seventeen fold since the first invention of these engines; and increased nearly threefold within twenty years.
There is now an engine at the mines called the Fowey Consols in Cornwall, of which Mr. Taylor considers the average duty, under ordinary circumstances, to be above 9,000,000; and which has been made to lift 97,000,000 lbs of water one foot high, with one bushel of coals.
The effect of these improvements on the operations of mines, in facilitating their drainage, has been of inestimable importance in extracting metals from depths which otherwise could never have been reached. Mines which had been stopped from want of power, have been reopened, others have been materially deepened, and a mass of mineral treasure has been rendered available, which without these engines must have been for ever inaccessible.
It results from these rapid advances in the application of coal to the production of power, and consequently of wealth, that mining operations of vast importance, have been conducted in Cornwall at depths till lately without example, e. g. in Wheal Abraham, at 242 fathoms, at Dolcoath at 235 fathoms, and in the Consolidated Mines in Gwennap at 290 fathoms, the latter mines giving daily employment to no less than 2,500 persons.
In the Consolidated Mines, the power of nine steam engines, four of which are the largest ever made, having cylinders ninety inches in diameter, lifts from thirty to fifty hogsheads of water per minute, (varying according to the season) from an average depth of 230 fathoms. The produce of these mines has lately amounted to more than 20,000 tons of ore per annum, yielding about 2,000 tons of fine copper, being more than one seventh of the whole quantity raised in Britain. The levels or galleries in these mines extend in horizontal distance a length of about 43 miles. (See J. Taylor's account of the depths of mines, third report of British Association, 1833, p. 428.)
Mr. J. Taylor further states, (Lond. Edin. Phil. Mag. Jan. 1836, p. 67) that the steam engines now at work in draining the mines in Cornwall, are equal in power to at least 44,000 horses, one sixteenth part of 3 bushel of coals performing the work of a horse.
