J. N. Lockyer—New Method of Spectrum Observation. 311 
5. We have the power of determining the lower states by 
means of absorption phenomena and then of observing the ra- 
diation of the vapors produced by the passage of a feeble cur- 
rent of electricity. 
Ezxample.—The fluted spectrum of sodium described by 
Roscoe and Schuster is instantly abolished by this means and 
a brightening of the green and a considerable thickening of 
. the dark yellow lines is seen. 
. we consider the existence of these molecular states as 
forming a true basis for Dalton’s law of multiple proportions ? 
if so, then the metals in different chemical combinations will 
exist in different molecular groupings, and we shall be able by 
spectrum observations to determine the particular heat-level to 
which the molecular complexity of the solid metal induced by 
chemical affinity corresponds. 
xamples.—None of the lines of magnesium special to the 
flame spectrum are visible in the spectrum of the chloride 
either when a flame ora spark is employed. e facts re- 
corded in my papers, printed in the Philosophical Transactions 
some years ago, on the spectra of salts and mixtures, seem all 
explained in this way. 
I think then that the method of mapping, to be complete, 
should not only show the metallic lines as produced at various 
temperatures compared with the Fraunhofer ones, but that for 
each metal investigations should be made and recorded for as 
many heat-levels as possible, and for various chemical group- 
ings such as 
Cr O Fe,Cl, 
Cr O, Fe Cl, 
Cr,O, Fe 
Cr, 
to give examples, with a view of investigating the facts, to see 
whether we can trace a molecular evolution in each case. 
