COAL).
Of the quantity of "mineral" raised at the collieries of Great Britain, it is estimated that 2.9% is refuse, but from this refuse 4.7% is recovered in the form of coal.
The figures for the year 1917 were as follows:— Tons Gross output . . Refuse . . . or 2.9% of gross output.
Coal recovered from refuse . . or 4.7% of the refuse.
There would appear to be room also for the introduction of methods of saving coal in the process of cleaning.
The consumption of fuel for the production of power at mines amounted in 1917 to nearly 17,000,000 tons, or 6.2% of the out put. Under a system of the generation or transmission of electrical energy "in bulk," with, consequentially, the most perfect means of fuel consumption, the probability is that the power necessary to work the collieries could be provided with a coal consumption of one-third that of the present amount, or result in a saving of about 10,000,00o tons of coal annually. It must be borne in mind, however, in this connection that the coal consumed in raising steam at collieries is frequently refuse and of such poor quality as to be difficult of disposal otherwise.