Elements of theoretical and descriptive astronomy, for the use of colleges and academies (1901)
White, Charles J · New York: J. Wiley & sons · leaf 49
[See Note A, page 268.] 42 SEXTANT. THE SEXTANT. 40. The stxtant is an instrument by which the angular (listance between two visible objects may be measured. It is usedchiefly by navigators; but its portability gives it great valuewherever celestial observations are required. The angles forthe… … Kg. 14. of a sector of a circle, the arc of which comprises 60°. A movablearm, CD, called the index-bar, revolves about the centre of thesector. This bar carries at one extremity a vernier, D. At theother extremity of the index-bar, and revolving with it, is placeda silvered mirror, C, the surface…
Astronomy
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![An illustration from Declaration de l'vsage du graphometre : par la pratique duq[ue]l l'on peut mesurer toutes distances des choses de remarque qui se pourront voir et discerner du lieu ou il sera posé : et po[ur] arpenter terres, bois, prez, & faire plans de villes et forteresses, cartes geographiques, & generalement toutes mesures visibles : et ce sans reigle d'arithmetique (1597)](https://img.insideoutlibrary.com/img/200/ia-declarationdelvs00danf-12-3.webp)
