Scientific amusements . n a vertical stem, fixed on apedestal, on which it turns >vith ease. Each panel con-tains a zpotroptic design, and the impression of eachfigure on the retina gives the spectator the idea of asingle figure with different action ; at the different periodsof a movement comprised between its extreme limits. Fig. 72.—The Silhouette Portraits. THE SILHOUETTE PORTRAITS. Take a large sheet of paper, black on one side andwhite on the other. Fix it by means of pins to the wallso that the white surface is outermost. On a table closeby place a good lamp, and let the person whose
Scientific amusements . n a vertical stem, fixed on apedestal, on which it turns >vith ease. Each panel con-tains a zpotroptic design, and the impression of eachfigure on the retina gives the spectator the idea of asingle figure with different action ; at the different periodsof a movement comprised between its extreme limits. Fig. 72.—The Silhouette Portraits. THE SILHOUETTE PORTRAITS. Take a large sheet of paper, black on one side andwhite on the other. Fix it by means of pins to the wallso that the white surface is outermost. On a table closeby place a good lamp, and let the person whose portrait 7 86 LIGHT. you wish to take stand between the lamp and the sheetof white paper. You can then outline the proiile with apencil. Cut out the design, and, turning the paper, gumthe drawing black side outwards on another sheet of(white) paper. Your portrait will then be mounted, andthe sillwttette will show very well in black. TO VARY THE SIZE OF A HALFPENNl,Take a rectangular box of white wood, and in one side. Fig Mode of EquaHzing llie size ot larger and smaller Coins. of it fix a nail or bodkin, to which attach, with wax orother substance, a halfpenny. Beside this halfpenny, buton the surface of the box; fasten a farthing.; If you gazeat these two pieces of money through- a small, circularhole in a piece of cardboard (as in Fig. 73), you will notbe able to distinguish one coin from the other. Theywill both appear the same size. lJlK&lSi^lSJ^^CE OF IMPRESSIONS OF THE RETINA. 87 Of course the distance at which the coin^ must beplaced will depend upon the powers of vision of thespectator. It is as well to fix the cardboard screen, andthen move the box farther or nearer, as may be time will come when the two coins will appear ofequal size; but by gradually lessening, the distance thefarthing will actually appear larger than the experiment demonstrates that the eye under theconditions indicated is unable to appreciate the distancebetween
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Keywords: ., bookcentury1800, bookdecade189, booksubjectscientificrecreations
