PHILOSOPHICAL TRANSACTIONS. 
I. On the Spectra of Ignited Gases and Vapours, with especial regard to the different 
Spectra of the same elementary gaseous substance. By Dr. J. Plucker, of Bonn, 
For. Memb. B.S., and Dr. J. W. Hittorf, of Munster. 
Received February 23, — Read March 3, 1864. 
1. In order to obtain the spectra of all the elementary bodies, you may make use either 
of flame or the electric current. For this purpose flame is preferable on account of its 
easy management, and therefore was immediately introduced into the laboratory of the 
chemist. But its use is rather limited, the metals of alkalies being nearly the only sub- 
stances which, if introduced into flame, give spectra exhibiting well-defined bright lines. 
In the case of the greater number of elementary substances the temperature of flame, 
even if alimented by oxygen instead of air, is too low. Either these substances are 
not reduced into vapour by means of flame, or, if reduced, the vapour does not reach the 
temperature necessary to render it luminous in such a degree that by prismatic analysis 
we obtain its characteristic rays. The electric current, the heating-power of which may 
be indefinitely increased by increasing its intensity, is alone fitted to produce the pecu- 
liar spectra of all elementary bodies. 
2. In applying the electric current we may proceed in two ways. In one mode of 
proceeding the substance to be examined by its spectrum is at the same time, by means 
of the current, transformed into vapour and rendered luminous. In the other mode 
the substance is either in the gaseous state, or, if not, has been converted into it by 
means of a lamp, and the electric current ignites the substance in passing through. 
3. The first way of proceeding is the least perfect, but we are obliged to recur to it 
in the case of all such elementary bodies as neither by themselves nor combined with 
other substances can be vaporized without altering the least-fusible glass. If the sub- 
stance to be examined be a metal, the extremities of the conducting- wires are made of 
it and placed at a short distance from one another. When the strong spark of a large 
Leyden jar, charged by Ruhmkorff’s powerful induction-coil, is sent through the space 
between the two extremities of the conducting-wires, minute particles of the metal, 
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