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 . and will be longer than a space on the circle by 1, to which it willtherefore read, as in the last case, but the Vernier will be retro-grade. This is the Vernier of the compass, Fig. 148. The pecu-liar manner in which it is there applied is sho^-n in Fig. 15 spaces on the Vernier are equal to 16 on the circle, each 16 X 30space on th
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 . and will be longer than a space on the circle by 1, to which it willtherefore read, as in the last case, but the Vernier will be retro-grade. This is the Vernier of the compass, Fig. 148. The pecu-liar manner in which it is there applied is sho^-n in Fig. 15 spaces on the Vernier are equal to 16 on the circle, each 16 X 30space on the Vernier will be = —ij-;^— = 32, and the Vernier 15 will therefore read to 2. ^ (351) Circle divided to 20. If 20 spaces on the Vernierare equal to 19 on the circle, each space of the latter will be =19 X 20 ^ ^^,^ ^^^ ^^^ Vernier will read to 20— 19 = 1. If 40 spaces on the Vernier are equal to 41 on the circle, each 41 X 20 = 20V;andtheVer- space on the Vernier will be =nier will therefore read to 20^ 40 ^ 20 = 30. It wiU be retro-grade. In the following figure the reading is 360, or 0° ; and itwill be seen that the 40 spaces on the Vernier (numbered to wholeminutes) are equal to 13° 40 on the limb, i. e. to 41 spaces, eachof 20. If 60 spaces on the Vernier are equal to 59 on the circle, each 59 X ^0of the former will be = —^-^- = 19 40, and the Vernier bU 236 TRAi\SIT AlVD THEODOLITE SURVEYING. [part iv will therefore read to 20 —19 40 = 20. The foUowmg figureshows such an arrangement. The reading in that position -wouldbe 40 46 20. Fig. Q34.
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectsurveying, bookyear18
