Levelling, and Its General Application

Levelling, and Its General Application

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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. 1887 edition. Excerpt: ...always necessary to limit the forward observation to the outer boundary of it, as it is difficult, and at times impracticable, without the aid of an artificial light, to read the staff within it; whereas there will be no difficulty in reading a staff held on the outside of its limits when the instrument itself is erected within; neither will there be any difficulty in reading the staff within the limits when the instrument and staff are alike situated in the general shade. On some works the track through woodland is cleared. An expeditious leveller sets up his instrument quickly, quickly removes it, and nearly always sets it up on the most advantageous site. I do not, however, advise the beginner, when levelling upon very steep or undulating ground, to endeavour to erect the instrument to such a degree of nicety as to be able, by a double observation, to read within an inch or two of both extremities of the staff, because such an endeavour would probably result in failure, and entail a re-setting up of the instrument, and consequently a loss of time. He would do well to erect it so as to be quite sure of being able to read his first back sight, thus entering as it were into a kind of compromise between certainty and rapidity, and leaving time and experience to guide him hereafter. Figs. 29, 30, and 31 are illustrative of the erection of the instrument in the most economical positions. At the conclusion of the first chapter, I explained that the errors due to the curvature of the earth were balanced by the method of using the spirit level on the tripod; yet it may be well to make exceptions to the rule, which does not strictly apply when levels are taken along continuous lines of ascent and descent. Reference to Fig. 32 will show that in levelling...show more

Product details

  • Paperback | 32 pages
  • 189 x 246 x 2mm | 77g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236554655
  • 9781236554659