Transactions of the Australasian Institute of Mining Engineers Volume 4-5

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1897 Excerpt: ...Similarly, the distance from the Main reef leader to the South reef, which is only about 5o feet in the "Salisbury," is over 1oo feet at some points in the " Robinson." Naturally the varying dips encountered have much to do with the horizontal distance as between reef and reef, but setting that factor aside, there is an important variation in the thickness of the sandstones between the interbedded reefs. The practical bearing of this relation is that whilst one level is sufficient when the reefs lie closely together, two are necessary when they are separated by any appreciable width of sandstones. Having thus briefly stated the general features of the ore deposits, I now pass on to the matter under immediate consideration, namely, "Shafts." Almost without exception the shafts on the Witwatersrand are of rectangular section. Only in one or two cases have circular shafts been adopted, and those in quite the "early days" of the industryes development. Many advantages are claimed for them by men who have experienced their use in connection with coal mining, but the fact that they have not come into any favour upon the fields argues a want of any particular merit from the metalliferous mineres standpoint. Almost without exception the outcrop mines on these fields are worked by incline shafts, the number of which is determined by the len-th of outcrop which a given company holds. Should, for instance, a companyes boundaries include 5ooo feet of outcrop, two shafts would be sunk at about 1ooo feet from the eastern and western boundaries respectively. The properties of the earller formed componies are, however, much smaller in area than that instanced, as: --Wemmer, 15oo feet on strike. Salisbury, 9oo feet on strike. Ferr...