. Animal and vegetable physiology considered with reference to natural theology. Natural theology; Physiology; Plant physiology; Biology. VISION. 409 with tolerable exactness, to produce the con- vergence of parallel rays to a focus; and by making. the denser medium convex on both sides (as shown in Fig. 410), both surfaces will conspire in pro- ducing the desired effects. Such an instrument is termed a double convex lens; and it has the pro- perty of collecting into a focus rays proceeding from distant points. Having obtained this instrument, we may now venture to enlarge the aperture through
. Animal and vegetable physiology considered with reference to natural theology. Natural theology; Physiology; Plant physiology; Biology. VISION. 409 with tolerable exactness, to produce the con- vergence of parallel rays to a focus; and by making. the denser medium convex on both sides (as shown in Fig. 410), both surfaces will conspire in pro- ducing the desired effects. Such an instrument is termed a double convex lens; and it has the pro- perty of collecting into a focus rays proceeding from distant points. Having obtained this instrument, we may now venture to enlarge the aperture through which the light was admitted into our dark chamber, and fit into the aperture a double convex lens. We have thus constructed the m ell-known optical instrument called the Camera Obscura, in which the images of external objects are formed upon a white surface of paper, or a semi-transparent plate of glass; and these images must evidently be in an inverted posi- tion with respect to the actual objects which they represent. Such is precisely the construction of the eye, which is, to all intents, a camera obscura: for in both these instruments, the objects, the principles of construction, and the mode of operation are ex- actly the same; and the only difference is, that the former is an infinitely more perfect instrument than the latter can ever be rendered by the utmost efforts of human 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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