648 
ME. J. NORMAN LOCKYER ON SPECTRUM-ANALYSIS 
a more intense spectrum the higher the temperature of the flame. In the same flame, 
those of the compounds of a metal give the brightest spectra which are most volatile. 
“ In order to prove still more conclusively that each of the above-mentioned metals 
always produces the same bright lines in the spectrum, we have compared the spectra 
represented in the Plate with those produced when the electric spark passes between 
electrodes made of these metals. 
“ Small pieces of sodium, potassium, lithium, strontium, and calcium were fastened to 
fine platinum wires and melted two by two into glass tubes, so that the pieces of metal 
were separated by about 1 to 2 millims., and the platinum wires were melted through 
the sides of the glass tubes. Each of these tubes was placed in front of the spectrum- 
instrument, and by meansof a Ruhinkorff’s induction-apparatus*, sparks were allowed 
to pass between the pieces of metal inside the tube ; the spectrum thus produced was 
then compared with that given by a gas-flame in which the chloride of the metal was 
brought. The flame was placed behind the glass tube. By alternately bringing the 
induction-apparatus into and out of action, it was easy, without measuring, to convince 
ourselves that in the brilliant spectrum of the electric spark, the bright lines of the 
flame-spectrum were present in their right position. Besides these lines, other bright 
ones appeared in the electric-spark spectrum ; some of these were produced by foreign 
metals present in the electrodes, others arose from nitrogen, which filled the tubes after 
the oxygen had combined with a portion of the electrodes ”f. 
As already mentioned in a note, the Plate given with this communication shows that 
the spectra thus referred to by the illustrious German chemists were the flame-spectra 
of the elements in question. 
This question was advanced in 1862 by Mitscherlich J and by Professors Roscoe and 
Clifton^, from whose memoirs I proceed to give extracts, and in 1865 by Diacon[[. 
Mitscherlich, in his memoir, after detailing some experiments, goes on to remark : — 
“ It follows from these experiments that metallic compounds do not always give a 
spectrum, and that in the case of those that do, the spectra are not always the same ; 
and, further, that the spectra are different when they are due to a metal or its combina- 
tions. We have also the right to conclude that each binary compound which gives a 
spectrum gives one peculiar to itself, excepting always of course when the combination 
is destroyed by the flame. Up to the present time we are acquainted with little beyond 
the spectra of the metals themselves, by reason of the facility with which the flame 
reduces their combinations. 
“ Up to the present time also it has been admitted that metals always give the same 
spectra with whatever they are combined^]". As in the above experiments this was not 
* No mention is made of a jar, which doubtless was not employed. 
f I shall produce evidence in the sequel to show that this explanation is probald}' not the correct one. 
+ Ann. de Chim. et de Phys. 1862, p. 175. 
§ Trans. Lit. and Phil. Society, Manchester, 1862. 
|| Annales de Chimie et de Physique, 4 ser. vol. vi. p. 5. 
il This is a reference to Kirchhoff’s and Bunsen’s paper just quoted. 
