. The art of projecting. A manual of experimentation in physics, chemistry, and natural history, with the porte lumière and magic lantern. the distillation of petroleum and coaltar, and are not in the market. The Aurora tube and Geisler tubes when lighted bythe electric spark may be used to obtain fluorescenteffects. With the former, writing and drawings madewith proper solutions, may be seen when such markingswould be entirely invisible in common white tubes are often made to contain some prettydesign in uranium glass, or there is some vessel con-taining a fluorescent solution s
. The art of projecting. A manual of experimentation in physics, chemistry, and natural history, with the porte lumière and magic lantern. the distillation of petroleum and coaltar, and are not in the market. The Aurora tube and Geisler tubes when lighted bythe electric spark may be used to obtain fluorescenteffects. With the former, writing and drawings madewith proper solutions, may be seen when such markingswould be entirely invisible in common white tubes are often made to contain some prettydesign in uranium glass, or there is some vessel con-taining a fluorescent solution surrounded with a jacketfilled with some gas which gives a violet light likenitrogen. A very beautiful effect is produced by exposing anumber of highly fluorescent media to the flame ofsulphur burning in oxygen in a dark room. 126 THE ART OF PROJECTING, DOUBLE REFRACTION. A piece of calc spar will be needed to show size is not very material, though the thicker it isthe farther apart will the refracted figures be. Itshould have smooth faces, but the natural faces areoften good enough to permit this phenomenon to Fig> 94. Make a hole a quarter of an inch in diameter througha bit of cardboard (unless you chance to have a dia-phragm with holes of various sizes) and place it at theaperture; the small beam of light which comesthrough it should be directed horizontally upon thescreen. Next place the piece of spar in front of it,and then project the hole with an object lens with afoot or more focus. The two spots will appear uponthe screen, and if the spar be rotated the one spotwill revolve about the other. Instead of the hole in adiaphragm, it will do as well to make a black spot upona piece of glass and project it in the same way. Either side of the spar may be used for showingthis phenomenon. A double-image prism may also be used with stillbetter results as the images will be still further separated. LIGHT. 127 POLARIZATION OF LIGHT. Plane-polarized light
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Keywords: ., bookcentury1800, bookdecade1870, bookpublisherbosto, bookyear1877
