An introduction to the present practice of surveying and levelling ; With an appendix, containing such arithmetical rules and examples as are necessary for the explanation of the subject

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. 1846 Excerpt: ...lines. The long lines represent each one hundredth of an inch, and the short lines each two thousandths of an inch. If the zero stands in a line with one of the subdivisions. 5 hundredths must be added to the number of tenths below zero. Suppose it stood at the subdivision above the sixth long line between 30 and 31 (B in the cut), then the reading would be 30 inches 6 tenths, and 5 hundredths (30-65 inches). If the zero should not meet any line on the scale, then observe what line on the vernier coincides with one on the scale, the long lines on the former representing hundredths, and the short ones each two thousandths. Suppose the line marked 3 on the vernier cut one of the lines on the scale (C in the cut), then there would be three hundredths to be added to the reading of zero on the scale--thus: Reading of zero on the scale.. 30-65 Reading of vernier '03 Total 30-68 inches. 30 B If the line marked D in the cut coincided with one of the lines on the scale, then the reading of the vernier would be three hundredths six thousandths, each of the three small divisions above the 3 on the vernier being two thousandths; the reading of the instrument would consequently be--Beading of zero on the scale.. 3065 Eeading of vernier '036 ON THE THEODOLITE. The theodolite is an instrument used in surveying, for measuring both horizontal and vertical angles. It is of great value in determining important stations, and in running base lines, being the most perfect of all angular instruments. Plate 8 represents Troughton and Simm's 5-inch theodolite. It is composed of a horizontal limb for measuring horizontal angles, with compass and spirit levels, parallel plates and screws for levelling it; and a vertical limb for taking vertical angles, with telescope and a spirit lev...