An introduction to astronomy : designed as a text book for the students of Yale College (1846)
Olmsted, Denison, 1791-1859, Yale College (1718-1887) · New York : Collins, Brother & Co. · leaf 83
nstrument is supportedon a tripod, for the sake of greater steadiness, each foot beingfurnished with a screw for levelling. 129. The sextant is one of the most useful instruments, bothto the astronomer and the navigator, and will therefore meritparticular attention. In figure 19,1 and H are two… … the Index Glass and H the Horizon Glass. The under part onlyof the horizon glass is coated with quicksilver, the upper partbeing left transparent; so that while one object is seen throughthe upper part by direct vision, another may be seen throughthe lower part by reflexion from the two mirrors.…
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-106-26.webp)
