The geography of the heavens, and class-book of astronomy: (1858)
Burritt, Elijah H. (Elijah Hinsdale), 1794-1838, Mattison, Hiram, 1811-1868 · New York, Mason brothers · leaf 311
; but the other being lessconvex, the focus is more distant. 616. The distance of thefocus of a double-convex glasslens is the radius of the sphereof its convexity. In this cut, it will be seen that theparallel rays A are refracted to a focusat C, by the double-convex lens B, theconvexity of whose… … DOUBLE CONVEX—FOCAL DISTANCE.
Constellations · Stars
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