J. N. Lockyer—New Method of Spectrum Observation. 808 
quired direction by adopting a method of work with a spark and 
a Bunsen flame, which Col. Donnelly suggested I should use 
with a spark and an electric are. This consists in volatilizing 
those substances which give us flame spectra in a Bunsen flame 
and passing a strong spark through the flame, first during the 
rocess of volatilization, and then after the temperature of the 
: me has produced all the simplification it is capable of pro- 
ucing, 
The results have been very striking; the puzzles which a 
comparison of flame spectra and the Fraunhofer lines has set 
us find, I think, a solution; while the genesis of spectra is 
made much more clear. 
case, and from the dissimilarity in the other, we may imagine 
that in the former case—that of sodium—we are dealing with a 
ty easily broken up, while lithium and potassium are more 
resistant; in other words, in the case of sodium, and dealing 
only with lines recognized generally as sodium lines, the flame 
as done the work of dissociation as completely as the sun it- 
Now it is easy to test this point, for if this be so then (1) 
the chief lines and flutings of sodium should be seen in the 
flame itself and (2) the spark should pass through the vapor 
after complete volatilization has been effected without any vis- 
ible effect. 
Observation and experiment have largely confirmed these 
predictions, Using two prisms of 60° and a high-power eye- 
Plece to enfeeble the continuous spectrum of the densest vapor 
Produced at a high temperature, the green lines, the flutings re- 
corded by Roscoe and Schuster, and another coarser system of 
flutings, so far as I know not yet described, are beautifully seen. 
say largely, and not completely, because the double red line 
and the lines in the blue have not yet been seen in the flame, 
either with one, two or four prisms of 60°, though the lines are 
seen during volatilization if a spark be passed through the flame. 
Subsequent inquiry may perhaps show that this is due to the 
sharp boundary of the heated region, and to the fact that they 
Tepresent the vibrations of molecular groupings more complex 
eg i i triplets, their change into quar- 
lets, = ddl peobebiiiey inte | Bes tomercnpnacted venbagg of flutings into lines, 
by iner easing the rate of dissociation. 
