Journal - Franklin Institute of the State of Pennsylvania (1826)
Franklin Institute, Philadelphia, Franklin Institute (Philadelphia, Pa.) · [Philadelphia : Franklin Institute] · leaf 398
, strictly speaking, lenses. The diverging lenses, whichare thinner in the centre than at their margin, are : The double con-cave, with both surfaces concave; the piano concave, with one surfaceplane, the other concave; and the concave convex, with a concaveand a convex surfcice, the concave having… … The general properties of lenses, which are of importance, are:first, the principal axis; second, the optical centre ; third, the prin-cipal and conjugated foci; and fourth, the nodal points or conjugatedcentres. A straight line, drawn through the centres of curvature ofthe spherical surfaces of a…
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