Wentworth, G. A. (George Albert), 1835-1906 · Boston, Ginn · leaf 26
form of the vernier is known as the retrograde form,since the figuring on the vernier proceeds in the opposite direc-tion from that on the scale. In either form the followingrule for using and reading the vernier may be adopted: Move the vernier tintil its zero line, or index, is at the pointto… … Fig. 12 Compass Vernier and its Uses. Let LL (Fig. 12) repre-sent the limb of the compass graduated to half degrees, andVV the vernier divided into thirty equal spaces, equal totwenty-nine spaces of the limb. Then, one space of the vernieris less than one space of the limb by l(=30 — J^ of…
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