The theory and practice of surveying. Designed for the use of surveyors and engineers generally, but especially for the use of students in engineering (1886)
Johnson, J. B. (John Butler), 1850-1902 · New York, J. Wiley & sons · leaf 50
Fig. 5. In Fig. 5 are shown two direct verniers, such as are usedon transits with double graduations. Thus in reading to theright the reading is 138° 45^ but in reading to the left it is 221°15^ In each case we look along the vernier in the direction ofthe graduation for the coincident lines. … Fig. 6. In Fig. 6 is shown a special form of retrograde vernier inwhich the same set of graduation-lines on the vernier serve for 20 SURVEYING. either right- or left-hand angles. Here a division of the vernieris larger than a division on the limb, and it must therefore beread backwards. Thus, we…
Surveying
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