. The art of projecting. A manual of experimentation in physics, chemistry, and natural history, with the porte lumière and magic lantern. T\g. 73. beam till it reaches the water, where its direction willbe seen to change, becoming more perpendicular. Re-flect the beam upon the water at various angles ofincidence and mark the course of the refracted rays. In place of the small tank take a beaker, or anyvessel with square glass sides, and reflect the beamupon the surface of the water as before. The experiment may be varied by filling the vesselhalf full of water, then carefully pouring strong a
. The art of projecting. A manual of experimentation in physics, chemistry, and natural history, with the porte lumière and magic lantern. T\g. 73. beam till it reaches the water, where its direction willbe seen to change, becoming more perpendicular. Re-flect the beam upon the water at various angles ofincidence and mark the course of the refracted rays. In place of the small tank take a beaker, or anyvessel with square glass sides, and reflect the beamupon the surface of the water as before. The experiment may be varied by filling the vesselhalf full of water, then carefully pouring strong alcoholupon it to the depth of an inch or two, being carefulnot to mix them while pouring, and some ether uponthe; alcohol in the same careful way. Sending now thebeam through them as before, the different refractivepowers of the various liquids will be seen. Heated Fig. 74, LIGHT. 99 In the diverging beam from the lens hold aheated poker or any well heated body at a. Theair that is heated in its neighborhood will so deflectthe rays of light as to make quite a fine appearanceof heat upon the screen. An alcohol lamp lightedand held there will have its whole projection uponthe screen: the lamp and flame in outline shadow,while the heated gases rising make an interestingpicture. To present a still more striking case, project a largesolar spectrum, as described on another page, and abouthalf-way between the prism and the screen hold thelighted alcohol lamp, moving it slowly along in thedifferent colors of the spectrum. 4 — Lenses. The refractive power of difTerent forms of lensesmay be shown by holding them in the beam ofparallel rays. The refractive power of a lens ofwater is seen by taking twowatch glasses or one watch glass,and a piece of plain glass a littlelarger, and bringing the two to-gether under the surface of space between thes
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Keywords: ., bookcentury1800, bookdecade1870, bookpublisherbosto, bookyear1877
