As an actual fact, in four years from the time of his writing the above, the Rand gold yield from 69 companies working amounted to 5,325,355 ozs., the total production being of the gross value of £10,583,616; so that, far from his estimate being too sanguine or exaggerated, it was a literal forecast of the actuality. He subsequently expressed the opinion that the full producing power of the Rand would be reached by the end of the century, when the output might be expected to exceed £12,500,000 per annum. As a matter of fact the total value of gold produced in the Transvaal in 1898 was over £15,000,000, most of which came from the Rand, and, had mining operations in 1899 not been interrupted by the war, the output in that year would have reached to over £18,000,000. Mr. Smith based his estimate on a working depth of 5200 feet, and on an area of the reef only 11 miles in extent, but since his time deep mining has been successfully prosecuted to 7000 feet. Inference and analogy, therefore, both afford strong support to the correctness of estimates, based on the results of past working, of the future gold contents of the Witwatersrand reefs, which estimates, as appears, are more likely to be under-reckoned than otherwise, from the sheer immensity of the subject, and from the necessarily imperfect knowledge of the potentialities of so huge a problem. 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.