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 country are the workings extensive. Africa is apparently the continent poorest in coal, though valuable workings have been developed at various points in British South Africa, e.g. at Kronstad, &c., in Cape Colony, at Vereeniging, Boksburg and elsewhere in the Transvaal, in Natal and in Swaziland. Australia possesses fields of great value, principally in the south-east (New South Wales and Victoria), and in New Zealand considerable quantities of coal and lignite are raised, chiefly in South Island.

The following table, based on figures given in the Journal of the Iron and Steel Institute, vol. 72, will give an idea of the coal production of the world:—

The questions, what is the total amount of available coal in the coalfields of Great Britain and Ireland, and how long it may be expected to last, have frequently been discussed since the early part of the 19th century, and particular attention was directed to them after the publication

of Stanley Jevons’s book on The Coal Question in 1865. In 1866 a royal commission was appointed to inquire into the subject, and in its report, issued in 1871, estimated that the coal resources of the country, in seams of 1 ft. thick and upwards situated within 4000 ft. of the surface, amounted to 90,207,285,398 tons. A second commission, which was appointed in 1901 and issued its final report in 1905, taking 4000 ft. as the limit of practicable depth in working and 1 ft. as the minimum workable thickness, and after making all necessary deductions, estimated the available quantity of coal in the proved coalfields of the United Kingdom as 100,914,668,167 tons. Although in the years 1870–1903 the amount raised was 5,694,928,507 tons, this later estimate was higher by 10,707,382,769 tons than that of the previous commission, the excess being accounted for partly by the difference in the areas regarded as productive by the two commissions, and partly by new discoveries and more accurate knowledge of the coal seams. In addition it was estimated that in the proved coalfields at depths greater than 4000 ft. there were 5,239,433,980 tons, and that in concealed and unproved fields, at depths less than 4000 ft. there were 39,483,844,000 tons, together with 854,608,307 tons in that part of the Cumberland coalfield beyond 5 m. and within 12 m. of high-water mark, and 383,024,000 tons in the South Wales coalfield under the sea in St Bride’s Bay and part of Carmarthen Bay.

In Table V. below column I. shows the quantity of coal still remaining unworked in the different coalfields at depths not exceeding 4000 ft. and in seams not less than 1 ft. thick, as estimated by seven district commissioners; column II. the total estimated reductions on account of loss in working due to faults and other natural causes in seams and of coal required to be left for barriers, support of surface buildings, &c.; and column III. the estimated net available amount remaining unworked.

As regards the duration of British coal resources, the commissioners reported (1905):—

“This question turns chiefly upon the maintenance or the variation of the annual output. The calculations of the last Coal Commission as to the future exports and of Mr Jevons as to the future annual consumption make us hesitate to prophesy how long our coal resources are likely to last. The present annual output is in round numbers 230 million tons, and the calculated available resources in the proved coalfields are in round numbers 100,000 million tons, exclusive of the 40,000 million tons in the unproved coalfields, which we have thought best to regard only as probable or speculative. For the last thirty years the average increase in the output has been 2% per annum, and that in the exports (including bunkers) 4% per annum. It is the general opinion of the District Commissioners that owing to physical considerations it is highly probable that the present rate of increase of the output of coal can long continue—indeed, they think that some districts have already attained their maximum output, but that on the other hand the developments in the newer coalfields will possibly increase the total output for some years.

In view of this opinion and of the exhaustion of the shallower collieries we look forward to a time, not far distant, when the rate of increase of output will be slower, to be followed by a period of stationary output, and then a gradual decline.”

According to a calculation made by P. Frech in 1900, on the basis of the then rate of production, the coalfields of central France, central Bohemia, the kingdom of Saxony, the Prussian province of Saxony and the north of England, would be exhausted in 100 to 200 years, the other British coalfields, the Waldenburg-Schatzlar and that of the north of France in 250 years, those of Saarbrücken, Belgium, Aachen and Westphalia in 600 to 800 years, and those of Upper Silesia in more than 1000 years.

Coal-Mining.

The opening and laying out, or, as it is generally called, “winning,” of new collieries is rarely undertaken without a preliminary examination of the character of the strata by means of borings, either for the purpose of determining the