Mine Surveying

Mine Surveying

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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. 1913 edition. Excerpt: ...to the secondary objec Fig. 118.--Diagram of prismatic telescope, used on Iransit shown in Fig. 117. tive at the end of the horizontal axis, the main telescope is pointed on a distant object, the interior prism is moved into place and the objective prism is rotated about its axis until the object is again cut by the horizontal wire. The line of sight through the secondary objective is now in the plane passing through the horizontal axis and the main telescope, and the vertical angles as read on the vertical circle are the true ones. "The interchangeable feature allows the prism to be used on whichever objective is best suited for the work to be done. This simplifies the adjustment by limiting it to that necessary for one position, and permitting it to be made wherever an observation is to be taken. If the object sighted on in making the adjustment of the prism is near, it may be necessary to rotate the telescope more or less than 90 about its horizontal axis in adjusting for alignment or to slightly shift the instrument about its vertical spindle in adjusting for vertical angles, in order to see the object the second time when viewed through the prism, but this will not affect the accuracy of the adjustment. OTHER DEVICES FOR TAKING STEEP SIGHTS Tilting the Transit.--When a steep sight is to be taken and the standard transit is the only instrument available, a line may be transferred to underground points by tilting the whole transit, so that the steep line of sight will clear the plates, Fig. 119. This scheme was used to transfer a line down a shaft 190 ft. deep.1 The two front legs of the tripod were shortened and the rear leg was clamped to a 300-pound casting. In using this method, the horizontal axis must be made exactly horizontal, ...show more

Product details

  • Paperback | 94 pages
  • 189 x 246 x 5mm | 181g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236509196
  • 9781236509192