. The art of projecting. A manual of experimentation in physics, chemistry, and natural history, with the porte lumière and magic lantern. n front, and then work in front of that; orstill better, remove both condenser and objective, theoutlines of shadows will be quite well defined with theelectric light, and witTi the lime light, but not with anyoil light. REFLECTION. The reflecting power of various surfaces can beshown by holding them in the path of the beam fromthe reflector. Common mirrors, plain glass, coloredglass, metals polished and unpolished, woods, horn,polished stones, paper, will
. The art of projecting. A manual of experimentation in physics, chemistry, and natural history, with the porte lumière and magic lantern. n front, and then work in front of that; orstill better, remove both condenser and objective, theoutlines of shadows will be quite well defined with theelectric light, and witTi the lime light, but not with anyoil light. REFLECTION. The reflecting power of various surfaces can beshown by holding them in the path of the beam fromthe reflector. Common mirrors, plain glass, coloredglass, metals polished and unpolished, woods, horn,polished stones, paper, will all exhibit difference in thisproperty. Reflection from the two surfaces of glass is seenupon the screen when the parallel rays from the firstmirror reach it. Then will always be seen two orthree indistinct images of the sun, side by side. When ^4 THE ART OF PROJECTING. the sun is near the horizon, so that the porte lumiertis nearly horizontal, more of these reflections will ap-pear, due to multiple reflections upon the surfaces ofthe mirror. These can be magnified a good deal inthe following way. Place the lens o at about its focal. Fig. 61. length distant from the orifice, and then hold anotherplane mirror r so that it will reflect the beam upon an-other screen s, moving the mirror r to such a place asto project the image of the orifice. It will be seen tobe double, and when the images overlap, the light willbe much brighter. Multiple reflections from the twosurfaces of the mirror r may be seen by holding it at asmall angle to the beam of parallel rays. A piece ofplate glass two or three inches square answers for thisexperiment. That the reflected beam moves through twice theangle of the incident beam, may be shown by holdingthe mirror r in the beam without the lens o. If themirror be perpendicular to the beam, the light will bereflected back through the aperture; turning the mirrorslowly when it is 45° to the incident light, the beamwill be overhead 90° ; when it has been
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Keywords: ., bookcentury1800, bookdecade1870, bookpublisherbosto, bookyear1877
