The geography of the heavens and classbook of astronomy; (1863)
Burritt, Elijah H. (Elijah Hinsdale), 1794-1838, Mattison, Hiram, 1811-1868, Whitall, Henry, 1819-1887? Celestial planisphere. [from old catalog] · New York, Mason brothers; Boston, Mason & Hamlin; [etc., etc.] · leaf 312
e plano-convex, or half a double con-vex lens; one side being convex and the otherplane. B is a plano-concave ; one surface being con-cave, and the other plane. C is a double-convex lens, or one that isbounded by two convex surfaces. I) is a double-concave lens, or a circular pieceof glass hollowed… … 615. A double-convex lensconverges parallel rays to apoint called the focus; andthe distance of the focusdepends upon the degree ofconvexity. In the first of these cuts, the lens isquite thick, and the focus of the rays isquite near; but the other being lessconvex, the focus is more distant. 616.…
Constellations · Stars
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