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XLIV. On the Electrical Light. By H. W. Dove*. 
INCE Fraunhofer first showed that the spectrum of the 
electric spark was distinguished from that of the light of the 
sun by a very bright line in the green, and a somewhat less lumi- 
nous one in the orange, its prismatic analysis has been com- 
pleted, especially by the investigations of Wheatstone, Masson and 
Angstro6m+. Wheatstone has shown that the lines are different 
according to the nature of the metals between which the spark 
passes; and that when it.is produced between two different 
metals, the spectrum exhibits combined the lines which are per- 
ceived when it is produced consecutively between similar balls of 
each of the metals, According to Angstrém, this also applies 
to similar balls formed of an alloy of the two metals. Masson 
has ascertained, that, leaving out of consideration the dissimi- 
larity of the spectrum in the employment of different metals, 
determinate lines appear as common to it; and from this it has 
appeared the most natural opinion, that the light of the spark is 
mixed, consisting of a direct production of light in the medium 
in which the spark is produced, and glowing particles carried 
forward from the balls between which the spark is transmitted, 
Fresh proofs in favour of this view have been obtained, especially 
by Angstrom, by the prismatic analysis of the sparks evolved in 
different gases. 
A composite phenomenon may be indirectly investigated by 
changing the constituents which enter into it, or by attempting 
to produce these in an isolated condition. Draper has shown 
that the spectrum of a glowing platinum wire contains no lines, 
so that it is white in the strict sense; whilst with regard to the 
true electrical light without phenomena of incandescence, we are 
only able to judge of its colour by the naked eye. The lumi- 
nous phenomena, known under the names of electrical brush, 
glow, and interruption of the spark, are so constant and so 
feebly luminous as to render an exact prismatic analysis ex~ 
tremely difficult, and in many cases even almost impossible. The 
judgement of the colour of a homogeneous luminosity is, how- 
ever, very delusive. The ordinary gas-flame which is yellow by 
day, and even the orange light of an oil-lamp, appear white in 
the dark. For this reason we may presuppose that the eye will 
only furnish an uncertain judgement as to the colour of the 
weaker electrical luminous phenomena. Many of these are so 
faint, that for their exact perception they require the exclusion. 
of every other source of light; and Prevost, as is well known, 
has already observed, that with coloured illumination the 
* Poggendorff’s Annalen, No. 6. 1857. 
t See Phil. Mag. vol. ix. p. 329. 
