. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. 3io OPTICAL PROJECTION potassium chlorate, 1 part shellac. For calcium : 2 partschalk, 10 parts potassium chlorate, 3 parts shellac. Forstrontium: 3 parts strontium nitrate, 1 part potassic chlorate,1 part shellac. For barium: 3 parts barium nitrate, 1 partpotassium chlorate, 1 part shellac. The shellac to be powderedseparately from the salts, which are also to be rubbed downto powder, and the two mixed previous to use with a horn orwooden spoon. These methods are superior in effect
. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. 3io OPTICAL PROJECTION potassium chlorate, 1 part shellac. For calcium : 2 partschalk, 10 parts potassium chlorate, 3 parts shellac. Forstrontium: 3 parts strontium nitrate, 1 part potassic chlorate,1 part shellac. For barium: 3 parts barium nitrate, 1 partpotassium chlorate, 1 part shellac. The shellac to be powderedseparately from the salts, which are also to be rubbed downto powder, and the two mixed previous to use with a horn orwooden spoon. These methods are superior in effect to the use of glassrods, or sticks soaked in solution; besides which- the manipu-lation of such sticks in a jet is a very ticklish operation. 179. Reversed Spectrum Lines.—The absorption by vapoursof the same rays which they emit, is usually shown by Reversal of SoUura Line As a dark line depends upon the absorbing vapour being lessbright than the light of similar wave-length emitted by theradiant, this experiment, of all others, is shown with markedsuperiority by the electric arc. Fig. 170 shows the most widely known arrangement, asadopted by Dr. Tyndall, except that two prism-bottles would THE SPECTRUM 3 be used. In front of the slit e through which parallel raysare sent from the condensers, is a Bunsen burner, g, in theflame of which is held an iron or platinum spoon I containinga good pellet of sodium, which should burst into vivid com-bustion with some white vapour, In front of the sodium isarranged a screen s with an aperture, to shade off all directsodium light from the screen—hence this experiment is notwell adapted for a direct prism. The light from the slit hasall to pass through the sodium flame before it reaches the
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Keywords: ., bookauthorwrightle, bookcentury1900, bookdecade1900, bookyear1906
