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214 On Daguerreotyping dark lines in the Solar Spectrum. 
the bands are well distributed among the colors of the spectrum. 
The colors also, observed in the aurora borealis, probably indicate 
the elements involved in that phenomenon. ‘The prism may 
also detect the elements in shooting stars, or luminous meteors. 
Since from the preceding observations, it is evident that the 
electric light, whether from the interrupted galvanic current, or 
rom the common electric machine, is principally resolved into 
several bright bands by the prism; and that the light, thus pro- 
uced by one elementary body, differs in the number, brilliancy 
suggested by Prof. Graham) of chemical affinity? If so, are there 
only two poles, a chlorous and a zincous, to each molecule—or, 
are there as many poles or combining surfaces as are indicated by 
the number of bright bands of its refracted light? And (if the 
undulatory theory of light may be depended on) would not these 
bands give an indication of the size of those surfaces or poles! 
On Daguerreotyping the dark lines in the Solar Spectrum. 
—Being desirous to know whether corresponding lines exist in 
the actinic rays, L adopted the following method. The sun’s rays 
were admitted into a dark chamber, between the edges of two 
pieces of sheet brass about eight inches in length and separated 
te the thirtieth of an inch, at one end, but in contact at the 
other. 
Near the outside of the aperture thus formed, was placed a 
large lens, five feet in focus. Near the focus of the lens in the 
chamber, the rays pass through a prism and through a secon 
lens of about 20 inch focus, which shows the dark lines very 
distinctly on white paper, at its focus, for rays coming from the 
slit. The prepared Dag type plate, placed in the focus and 
exposed for oue or two seconds, produces the effect. 
In the Dagu ype, which I send you there are two spectra 
caused by filing the brass slips so as to cause an aperture on side 
of the point of contact. Ihave placed the letters on the lines as 
given in Brewster’s Optics, 1837, page 79. They ‘would corres- 
oe with Prof. Draper’s (see this Journal, March, 1848) if the 
occupied the place of I. 
I could not see the spectrum farther than the breadth of the 
second broad line at I in the direction beyond that line, when 
looking through the prism and slit at the sun. But by receiving 
the spectrum on paper stained with alcoholic tincture of turmeric, 
several dark lines can be seen beyond these and the blue appears 
_to be changed to violet down to the line F. 
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