804 J. N. Lockyer—New Method of Spectrum Observation. 
eet bodies in homologous series are those volatilized at the 
owest temperatures; so that on subjecting a mixture of two 
“ie burner, and C a temperature lower than that of the Bunsen 
urner. 
A. Highest temperature. ©. Lowest temperature. 
nant of the spectrum of a lower temperature. 
To make this reasoning valid we must show then that the 
spark, or better still the arc, provides us with a summation 0 
the spectra of various molecular groupings into whic 
solid metal which we use as poles is successively broken up by ee 
action of temperature. 
We are not limited to solid metals; we may use their salts. 
In this case it is shown in the paper before referred tot that ™ 
very many cases the spectrum is one much less rich in lines. 
I have therefore attempted to gain new evidence in the T 
* Proc. Roy. Soc., vol. xxviii, p. 162. + Phil. Trans. 1873, p- 258: 
