Proceedings of the Lake Superior Mining Institute Annual Meeting Volume 16

Proceedings of the Lake Superior Mining Institute Annual Meeting Volume 16

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1911 edition. Excerpt: ...5 show tubes with acid, gelatine, compass, and North and South points marked, just as they are taken from the drill hole. I intend to have another goniometer made with horizontal circle to measure the course as well as vertical circle for the inclination, but have not had an opportunity to do so as yet. We have found the method described above very successful, and two tests at the same point almost always agree. When this is not the case more tests are made and so far we have always been able to ascertain which are wrong. We have made tests at a depth of 2000', but it would probably be difficult to go much deeper without using more insulating wrapping around the thermos bottle than is possible with a bottle and case of dimensions now used. The precautions to be taken are three in number: first, that the compass swings perfectly freely, that is, that it does not catch on the cage and that the gelatine keeps liqu1d long enough; second, that there is no local magnetic attraction in the rock formation; and third, that the compass is not affected by the steel drill rods or casing or by other iron in the hole. The first precaution is easily taken; the second can only be judged by a knowledge of the formation and by taking iests at different depths. If these are concordant there is probably no appreciable magnetic attraction. The third precaution is important. We use 20' of brass rods and so have no iron within 20' of the compass. Tests with 10', 20', 30' and 40' of brass rods at the same depth gave the same reading in a hole dipping 500 North 450 East so that 20' is conservative. The results of a second test with shorter lengths of brass rods at another point are given below: Length of Brass Rods. Inclination. Apparent Course, 1' 620 N6E 2' more

Product details

  • Paperback | 78 pages
  • 189 x 246 x 4mm | 154g
  • United States
  • English
  • black & white illustrations
  • 1236913442
  • 9781236913449