there is virtue-in a bushel of coals, properly consumed,
to raise seventy millions of pounds weight
a foot high. This is actually the average effect of
an engine at this moment working in Cornwall.
The ascent of Mont Blanc from Chamouni
is considered, and with justice, as the most toilsome
feat that a strong man can execute in two
days. The combustion of two pounds of coal
would place him on the summit.”
The power which man derives from the use of
mineral coal, may be estimated by the duty*
* The number of pounds raised, multiplied by the number
of feet through which they are lifted, and divided by the number
of bushels of coal (each weighing eighty-four pounds) burnt in
raising them, gives what is termed the duty of a steam engine, and
is the criterion of its power. (See an important paper on improvements
of the steam engine, by Davies Gilbert, Esq. Phil.
Trans. 1830, p. 121.)
It is stated by Mr. J. Taylor, in his paper on the duty of steam
engines, published it) his valuable Records o f Mining, 1829, that
the power of the steam engine has within the last few years been
so advanced by a series of rapid improvements, that whereas, in
early times, the duty of an atmospheric engine was that of
5,000,000 pounds of water, lifted one foot high by a bushel of
coal, the duty of an engine lately erected at Wheal Towan in
Cornwall, has amounted to 87,000,000 pounds; or, in other
words, that a series of improvements has. enabled us to extract
as much power from one bushel, as originally could be done
from seventeen bushels of coal. Thus, through the instrumentality
of coal as applied in the steam engine, the power of man
over matter has been increased 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
MINES AND MACHINERY. 5 3 3
done by a pound, or 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,
and can only be overcome by those enin
Cornwall, of which Mr. Taylor considers the average duty,
under ordinary circumstances, to be above 90,000,000; and which
has been made to lift 97,000,000lbs 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