File:Transactions (1871) (14590211798).jpg

Identifier: transactionsmining27amer (find matches)
Title: Transactions
Year: 1871 (1870s)
Authors: American Institute of Mining, Metallurgical, and Petroleum Engineers
Subjects: Mineral industries
Publisher: New York (etc.)
Contributing Library: Gerstein - University of Toronto
Digitizing Sponsor: University of Toronto

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very large area of ore, and willbecome in the future one of the heaviest producers on therange. Thus far mining has been confined to steam-shovelwork in one cut; but the rest of the property has been verythoroughly and systematically explored. Fig. 25 shows oneof the Mahoning shovels of the latest design. Discussion of Different Mining Methods. It will be seen from the descriptions and maps of the variousmines that there are several important points in which themethods of mining differ. Perhaps the first to attract atten-tion, had the maps of the mines at Hibbing been published,would have been the method of laying out the main haulage-drifts. Haulage-Drifts.—The Lake Superior Consolidated Mines fol-lows the method of diagonal drifts, while the Minnesota IronCo. has adopted the rectangular plan shown in the map of theFayal mine, Fig. 17. The latter company used the diagonalplan for the first level of the Auburn mine, but abandoned it METHODS OF IRON MINING IN NORTHERN MINNESOTA. 385
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386 METHODS OF IRON MINING IN NORTHERN MINNESOTA. iii driving the second level. The advantage of the diagonalplan lies in the facility it offers to tramming, since the dis-tances from the working-places to the shaft are shorter andmore direct, and all curves are very easy. Its disadvantage isthat the blocks of ore formed by the drifts are diamond-shaped,and if the sub-drifts, from which caving and slicing are done,are placed directly over the main drifts, it is more difficult tomine all of the ore than if the blocks were rectangular. Itwould be very difficult to slice away and cave a system of sub-drifts laid out on the diagonal plan, on account of the triangu-lar pillars that would be left at certain stages of the work; andfurthermore, it would be much more difficult for the men tokeep track of the ore, and to know just when all of a pillarhad been mined, since the angles between drifts would notbe right angles. The rectangular plan for sub-drifts, if rigidlymaintained,causes less lo

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