. The art of projecting. A manual of experimentation in physics, chemistry, and natural history, with the porte lumière and magic lantern. burn with a yellow blaze and awhite vapor, through which the light from the lanternmust pass. If this vapor is dense enough it will stoprays from the other light that have the same refrangi-bility; and as its own luminousness is not very great,it will leave a black line upon the screen in the placewhere the sodium line would appear if the light camefrom it. It will be best to have a screen a foot square with ahole through it, to set in front of the sodium f
. The art of projecting. A manual of experimentation in physics, chemistry, and natural history, with the porte lumière and magic lantern. burn with a yellow blaze and awhite vapor, through which the light from the lanternmust pass. If this vapor is dense enough it will stoprays from the other light that have the same refrangi-bility; and as its own luminousness is not very great,it will leave a black line upon the screen in the placewhere the sodium line would appear if the light camefrom it. It will be best to have a screen a foot square with ahole through it, to set in front of the sodium flame toprevent its light from falling upon the large screen andinjuring the effect. LIGHT. 123 FLUORESCENCE. Only blue or violet or ultra-violet rays are capable ofproducing this phenomenon, and these may be obtainedeither by passing common white light from the sun, orthe electric light, or the lime light, through a piece ofblue or violet glass or through a solution of ammonia,sulphate of copper; or, better still, by producing a purespectrum. The best effects are to be observed by usinga prism of great dispersive power, like FUj 93. When colored glass is to be used to obtain theviolet light, it suffices to place a lens of a foot focusnear the orifice and the glass just in front of solids and solutions may then be examinedat S. A piece of uranium glass or a solution of quin-ine in a test tube or bottle will exhibit; this propertyso that many can see it at the same time. It will bewell to use two bottles or beakers of clear glass, — oneto contain pure water and the other the solution ofquinine — and examine them side by side in this bluelight. The fluorescence will then be more noticeable. When artificial light is used in a lantern it will onlybe necessary to place the colored glass in front of thecondenser, as if to project a picture upon it, andotherwise use the light as with sunlight. Pictures are sometimes made of fluorescent material. 124 THE ART
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Keywords: ., bookcentury1800, bookdecade1870, bookpublisherbosto, bookyear1877
