. Animal and vegetable physiology, considered with reference to natural theology, by Peter Mark Roget ... Biology; Physiology; Plant physiology; Natural theology. VISION. 457 M, N, o, p, Q, represent the inclinations of the surfaces of a rarer medium, calculated to in- crease the convergence of the rays, that is to bring them to a nearer focus (f). The result of the continued change of direction in the refracting surface, is a regular curvilineal sur- face, which, in the present case, approaches very nearly to that of a sphere. Hence by giving these refractive media spherical surfaces, we adap
. Animal and vegetable physiology, considered with reference to natural theology, by Peter Mark Roget ... Biology; Physiology; Plant physiology; Natural theology. VISION. 457 M, N, o, p, Q, represent the inclinations of the surfaces of a rarer medium, calculated to in- crease the convergence of the rays, that is to bring them to a nearer focus (f). The result of the continued change of direction in the refracting surface, is a regular curvilineal sur- face, which, in the present case, approaches very nearly to that of a sphere. Hence by giving these refractive media spherical surfaces, we adapt them, with tolerable exactness, to produce the convergence of parallel rays to a focus, and by making the denser medium convex on both sides (as shown in Fig. 410), both surfaces will 410 m. conspire in producing the desired effects. Such an instrument is termed a double convex lens; and it has the property of collecting into a focus rays proceeding from distant points.* Having obtained this instrument, we may now * The refraction by spherical surfaces does not, strictly speak- ing, unite a pencil of parallel or divergent rays into a mathe- matical point, or focus; for in reality the rays which are near the central line are made to converge to a point a little more. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Roget, Peter Mark, 1779-1869. London : W. Pickering
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