The divergencies in the several estimates made from time to time in the past of the total gold available from the Rand banket beds have in part arisen from the sheer inability of those making the estimates to anticipate the striking developments which have successively been made. So far back as 1893, 325 millions, and subsequently 450 millions and 700 millions, have been adventured by various persons. The relative moderateness of these estimates, compared with more recent ones, is due, as in the case of that of Mr. Hamilton Smith, to the under-valuation of the potentialities of deep-level mining, which are only now becoming fully apparent. One of the more recent estimates—that of Mr. Bleloch—based on working depths of 3000 to 7000 feet, and taken over an area of fifty miles, embracing the district between Randfontein and Holfontein, computes an available gold yield of £2,871,000,000 sterling, or eight times as much as the estimate of 1893.

Although so enlarged, the total actually understates potentialities by being exclusive of possible discoveries beyond these limits, and also by the estimates being framed on the older ratios of gold recovery to ore tonnage, thus ignoring the application of the latest scientific methods to the treatment of the poorest ore, which would tend to enhance the results considerably. Apart from these limitations, this estimate of 2871 millions is made in the most systematic manner, from careful calculations, area by area, according to the thickness of the reefs, the tonnage per claim, and the value per ton as they have been shown from past working. The total tonnage of payable ore available is estimated at 1,378,000,000. The average gold value per ton of ore in the figures works out at 41s. 7d., but in the actuality this varies from 78s. in the richest mines down to actual loss in the least paying of low-grade ores. In these stupendous figures are included the contributions of the great deep-level mines, the growing proportions of whose contributions to the aggregate output is already becoming a noteworthy feature, while the extent of their development cannot be foreseen. Mining engineers are indeed already considering the specifications of equipments for negotiating depths deeper than 7000 feet, and even in 1899 the possibility of mining at 12,000 feet was considered. Certainly the mining of minerals in other parts of the world has shown the feasibility of operations at much greater depths than those mentioned.

MINES ON THE LINE OF REEF AT JOHANNESBURG
Photo by Wilson, Aberdeen

The ascertainment of the proximate gold contents of the Transvaal mining area leads up to the question, How and when is this stupendous wealth to be rendered available? In other words, what is likely to be the gold production in the several years from now on, and how long will this rate of production continue? or what are the chances of the early exhaustion of the mining industry? To take the last item first, it is the growing conviction of Rand mining engineers that the amount of available gold is only limited by the extent to which mining operations can be prosecuted below the surface. Mining engineers had up till recently generally agreed to fix a depth of 8000 feet as the utmost limit to which mechanical appliances and other circumstances will allow them to follow the descent of the reefs, and the available gold yield is calculated on this basis. But there is no finality in this statement of depth, and already, as we have remarked, engineers are calculating for deeper delvings, and 9000 and even 12,000 feet have been spoken of. This latter increase of 4000 feet—from 8000 to 12,000 feet—would alone augment the gold estimate by 50 per cent. For the rest, and retaining the 8000 feet limit estimate as the measure of the exhaustion of the present Rand, this is naturally controlled by the rate of production per year, which itself is dependent on the particular circumstances of the industry during the period in question.

The yearly production of gold from now onwards offers no insurmountable obstacle to a fairly exact appreciation. It is merely a rule of three calculation: if in the past, under given circumstances, working results have been as follows; in the future, with the same or like circumstances, the results will be such. Various computations from time to time have been made on these bases, among the most recent being those of Mr. Cooper-Key and Dr. Hatch in 1899, Mr. Goldring and Mr. Bleloch in 1901, and quite recently Messrs. Leggett and Hatch (on 47 miles of the Rand only, and working to depths of 4000 to 7000 feet). Mr. Cooper-Key’s forecast, which was made in 1899, was for the output of the three following years, the war not having then been anticipated. The basis of his calculation, like that of Mr. Goldring’s, was the number of stamps or the milling power employed. If in 1898, he argued, there were in work on the Central, Eastern, Far Eastern, and Western sections of the Rand 6000 stamps, at the end of 1899 this number would probably be increased by 165, or to a total of 6165; at the end of 1900 the increase made would be 1730 and the total 7895; at the end of 1901 the total would have risen to 9845; and at the end of 1902 to 11,785. On the basis of 1800 tons milled per stamp, of an average value of £2 per ton, and with an average number of stamps of 7000, 9000, and 10,500 in the three years, the output would have been: 1900, £25,200,000; 1901, £32,400,000; and 1902, £37,800,000. Mr. Goldring, who is the Secretary of the Johannesburg Chamber of Mines, likewise framing his calculation on certain yearly increases in the milling power, calculated that in the five years following the full resumption of mining operations, 17,000 stamps would be at work, or an increase of 11,000 on the number before the war. Allowing for a fall in the grade of ore milled, in consequence of cheaper methods permitting of a lower grade of ore to be dealt with, the 17,000 stamps, he considered, would produce at least £50,000,000 sterling a year. Writing before the war, and basing his estimate on observations made by Mr. Eckstein that in five years the number of stamps in working would be 12,000, Dr. Hatch, likewise following the milling power basis, calculated for a yearly gold production of £36,000,000. Mr. Bleloch’s opinion, taking the production in the nine working months of 1899 of £20,000,000 as a basis, is that the rate of production would probably double itself after the war. “If this be so,” he adds, “in fifty years’ time the product of the Rand will have reached over £2,000,000,000, and if such an accelerated progress is made, the whole of the vast amount now estimated may be dug out of the Rand within sixty or seventy years.” The latest estimate published, that of Messrs. Leggett and Hatch, going on the basis of the average increase of production of £4,000,000 per year in the three years before the war, and that the production in 1899—a broken year owing to the war—was £19,000,000, concludes that, allowing eighteen months from January 1, 1902, for the industry to be restored to the conditions existing in August 1899, a similar increase of production will bring the output to at least £30,000,000 per annum by June 30, 1906, and if this rate of production were to be maintained from then on, the total production of £1,233,560,700 would give a life from January 1, 1902, of forty-two years and a half. But as the production will decline gradually, instead of coming to a sudden stop, the life of the industry is likely to be prolonged for some considerable number of years beyond the period indicated. If, on the other hand, the annual output should exceed £30,000,000 for any considerable period, as is, perhaps, within the bounds of possibility, this would partially offset the extension of life due to the gradual decline of production. It is to be added, in explanation of Messrs. Leggett and Hatch’s estimate, that it contemplates working along a strike of forty-seven miles only, and to the restricted depth of from 4000 to 6000 feet.

The following tabulated comparison of these several estimates will assist their comprehension, it being explained that Mr. Bleloch’s estimate is reduced to the extent of 25 per cent. as a set-off for probably barren sections, &c.:—

Year.Mr. Cooper-Key (1899).Dr. Hatch (1899).Mr. Goldring (1901).Messrs. Leggett & Hatch (1902).Mr. Bleloch (1901).
£££££
1898......20,000,000......
1899.........19,000,00020,000,000
190025,200,000............
190132,400,000............
190237,800,000.........15,000,000
1903...... 50,000,000 each year 30,000,000 each year20,000,000
1904...36,000,00025,000,000
1905...... 35,000,000 each year
1906......
1907......
1908.........
1909.........
1910.........
1911.........
1912.........
1913.........
1914.........
1915......... 40,000,000 each year
1924.........
1925......... 45,000,000 each year
1934.........
1935............ 40,000,000 each year
1944............
1945............ 30,000,000 each year
1954............
1955............ 30,000,000 each year
1964............
1965............ 15,000,000 each year
1974............

These several estimates are of course to be looked upon merely as approximations, and they are, moreover, not framed on exactly the same bases. They, however, agree in the main that the 1899 output of roundly £20,000,000 will be increased to some point between £30,000,000 and £50,000,000 within a few years’ time, and maintained thereat, more or less continuously, for periods varying over 45 and 65 years. The production of the several estimates for the whole period gives an average of £37,000,000, which is only slightly higher than that of Mr. Bleloch, which is £35,714,285. This, consequently, is the handsome yearly output which the Rand mining industry offers in the near future—an amount which alone equals the total production of the whole world in 1897—if the circumstances are at least equal to those which previously prevailed.