Bauhaus-Universität Weimar

Titel:
The Art of Projecting. A Manual of Experimentation in Physics, Chemistry, and Natural History with the Porte Lumière and Magic Lantern
Person:
Dolbear, A. E.
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit39441/127/
122 THE ART OF PROJECTING. 
Lithium, and Copper are especially good for this work 
and give satisfactory spectra. 
When this monochromatic light frotai the stick of 
glass or the saturated solution of sodium chloride is 
made to appear, it will be a good time to give atten¬ 
tion to its effects upon other colors. Observe the 
faces of individuals, the colors of flowers, of ribbons, 
of pictures. It is a good plan to have prepared a set 
of strips of bright-colored papers, or ribbons, or the 
Newton’s disk, for exhibition in monochromatic light. 
REVERSED LINE. 
The dark sodium line is the only one that is ever 
projected, owing to the great difficulty there is in 
making the vapors of other substances sufficiently 
dense to absorb the powerful rays from the electric arc 
or of the lime light. With either, a pure spectrum 
must first be projected, and the slit should be nicely 
focussed, as described. — Then having provided a 
gas jet with Bunsen burner, or an alcohol lamp in 
front of the slit, hold in it a small iron spoon con¬ 
taining a lump of metallic sodium as large as a pea. 
It will take fire and burn with a yellow blaze and a 
white vapor, through which the light from the lantern 
must pass. If this vapor is dense enough it will stop 
rays 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 place 
where the sodium line would appear if the light came 
from it. 
It will be best to have a screen a foot square with a 
hole through it, to set in front of the sodium flame to 
prevent its light from falling upon the large screen and 
injuring the effect.
        

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