Scientific amusements . rs. If, on the other hand, the lightis very intense,—if, for example, the direct light of thesun passes through a small opening,—the rays minglewith each other, and are surrounded by aureola of rays,composed of numberless extremely fine lines, of all colours, possessing a much largerdiameter, and which we dis-tinguish by the name of theaureola of capillary rays. The radiating form of stars,and the distant light of street-Radiating image. kmps bclong to thc pre- ceding phenomena. If the eye is accommodated to agreater distance than that of the luminous point,—andfor this
Scientific amusements . rs. If, on the other hand, the lightis very intense,—if, for example, the direct light of thesun passes through a small opening,—the rays minglewith each other, and are surrounded by aureola of rays,composed of numberless extremely fine lines, of all colours, possessing a much largerdiameter, and which we dis-tinguish by the name of theaureola of capillary rays. The radiating form of stars,and the distant light of street-Radiating image. kmps bclong to thc pre- ceding phenomena. If the eye is accommodated to agreater distance than that of the luminous point,—andfor this purpose, if the luminous point itself is distant, weplace before the eye a slightly convex: lens,—we seeanother radiating image appear, which M. Hclmholtzrepresents thus : at c as it is presented to the right eye,and at d aS seen by the left. If the pupil is covered on one side, the side opposite tothe image of diffusion disappears ; that is to say, thatpart of the retinal image situated on the same side as the. DOUBLE IMAGES. 55 covered half of the pupil. This figure, then, is formed byrays which have not yet crossed the axis of the eye. Ifwe place the luminous point at a distance to which theeye can accommodate itself, we see. through a moderatelight, a small, round, luminous spot, without any ir-regularities. If the light, on the contrary, is intense, theimage is radiated in every position of accommodation, andwe merely find that on approaching nearer, the figurewhich was elongated, answering to a distant accommoda-tion, gradually diminishes, grows rounder, and gives placeto the vertically elongated figure, which belongs to theaccommodation of a nearer point. When we examine aslender, luminous line, we behold images developed, whichare easily foreseen, if for every point of the line wesuppose radiating images of diffusion, which encroach oneach other. The clearest portions of these images ofdififusion mingle together and form distinct lines, whichshow multiplied ima
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Keywords: ., bookcentury1800, bookdecade189, booksubjectscientificrecreations
