A treatise on land-surveying; comprising the theory developed from five elementary principles; and the practice with the chain alone, the compass, the transit, the theodolite, the plane table, &cIllustrated by four hundred engravings, and a magnetic chart . 10 Fig. 229. i 60 45 30. The above figure shows such an arrangement. The index, orzero, of the Vernier is at a point beyond 358°, a certain distance,which the coincidence of the third Ime of the Vernier (as indicated £HAP. II.] Verniers, 233 by the dotted and crossed line) shows to be 15. The whole read-mg is therefore 358° 15. If 20 spaces
A treatise on land-surveying; comprising the theory developed from five elementary principles; and the practice with the chain alone, the compass, the transit, the theodolite, the plane table, &cIllustrated by four hundred engravings, and a magnetic chart . 10 Fig. 229. i 60 45 30. The above figure shows such an arrangement. The index, orzero, of the Vernier is at a point beyond 358°, a certain distance,which the coincidence of the third Ime of the Vernier (as indicated £HAP. II.] Verniers, 233 by the dotted and crossed line) shows to be 15. The whole read-mg is therefore 358° 15. If 20 spaces on the Vernier are equal to 19 on the circle, theVernier can read to one-twentieth of a division on the circle,i. e. to 3. EngUsh compasses, or Circumferentors, are some-times thus arranged. If 60 spaces on the Vernier are equal to 59 on the circle, theVernier can read to one-sixtieth of a division on the circle, i. e. to 1. (350) Circle divided to 3j. Such a graduation is a verycommon one. The Vernier may be variously constructed. Suppose 30 spaces on the Vernier to be equal to 29 on the 29 X 30 circle. Each space on the Vernier will be 30 — = 29, and will therefore be less than a space of the circle by 1, to whichthe Vernier will then read. F;l-. 230.
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectsurveying, bookyear18
