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 . 15 10 I I III W 9 8 7 6: 5 4 3 2 1 /|\ f CHAH. II.] Verniers. 237 (353) Circle divided to 10. If 60 spaces on the Vernier beequal to 59 on the limb, the Vernier will read to 10. In thefollowing figure, the reading is 7° 25 40, the reading on thecircle being 7° 20, and the Vernier showing the remaining spaceto be 5 40. Fi^. 10 9 8 7 6
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 . 15 10 I I III W 9 8 7 6: 5 4 3 2 1 /|\ f CHAH. II.] Verniers. 237 (353) Circle divided to 10. If 60 spaces on the Vernier beequal to 59 on the limb, the Vernier will read to 10. In thefollowing figure, the reading is 7° 25 40, the reading on thecircle being 7° 20, and the Vernier showing the remaining spaceto be 5 40. Fi^. 10 9 8 7 6 5 4 3 2 1 y^S \ C354) Readmi? backwards. AVhen an index carrying a Ver-nier is moved backwards, or in a contrary direction to that inwhich the numbers on the circle run, if we wish to read the spa^ewhich it has passed over in this du-ection from the zero point, theVernier must be read backwards, (i. e. the highest number becalled 0), or its actual reading must be subtracted from the valueof the smallest space on the ciicle. The reason is plain ; for,since the Vernier shows how far the index, moving in one direc-tion, has gone past one di\ision line, the distance which it is fromthe next di\dsion line (wliich it may be supposed to have passed,moving in a contrary direction), TviU be the difference between thereading and the value of one space. Thus, in Fig. 229, page 232, the reading is 358° 15. But,counting backwards from the 360°, or zero point, it is 1° 45. Caution on this point is particularly necessary in using siT»aIlangles of deflection for railroad curves. 238 TR
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectsurveying, bookyear18
