SCIENCE. 
221 
This method of inquiry lias been tried also with potassium, 
calcium, and some other metals, and with metallic salts. 
With potassium and calcium we get the same inversion 
of phenomena, the yellow-green lines of potassium being 
seen without the red ; while in the case of calcium the blue 
line alone was seen. 
The fact that in these experiments we get, as before men- 
tioned, vapors which at one and the same time exhibit dif- 
ferent colors and different spectra at different levels in the 
tube, at once suggests the phenomena of fractional distilla- 
tion. 
It is also suggested, as a result of the application of this 
new method, that in the case of a considerable number of 
chemical substances not only the line spectrum is com- 
pound in its origin, as I suggested many years ago, but that 
a large number of the lines is due to molecular groupings 
To take an instance, the dame spectrum of sodium gives 
us, as its brighest, a yellow line, which is also of marked 
importance in the solar spectrum. The flame spectra of 
lithium and potassium give us, as their brightest, lines in 
the red which have not any representatives among the 
Fraunhofer lines, although other lines seen with higher 
temperatures are present. 
Whence arises this marked difference of behavior? 
From the similarity of the dame spectrum to that of the sun 
in one case, and from the dissimilarity in the other, we may 
imagine that in the former case — that of sodium — we are 
dealing with a body easily brokeu up, while lithium and 
potassium are more resistant ; in other words, in the case 
of sodium, and dealing only with lines recognized gener- 
ally as sodium lines, the dame has done the work of disso- 
i ciation as completely as the sun itself. Now it is easy to 
of considerable complexity, which can be kept out of re- 
action by careful low temperature distillation. 
So much then for one method. Now for the other. 
In this I have attempted to gain new evidence in the re- 
quired direction by adopting a method of work with a spark 
and a Bunsen dame, which Col. Donnelly suggested I 
should use with a spark and an electric arc. This consists 
in volatilizing those substances which give us dame spectra 
in a Bunsen dame and passing a strong spark through the 
dame, first during the process of volatilization, and then 
after the temperature of the dame has produced all the sim- 
plification it is capable of producing. 
The results have been very striking ; the puzzles which a 
comparison of dame spectra and the Fraunhofer lines has 
presented us find, I think, a solution ; while the genesis of 
spectrais made much more clear. 1 
1 I allude more especially to the production of triplets, their change 
into quartets, and in all probability into flutings, and to the vanishing of 
flutings into lines, by increasing the rate of dissociation. 
test this point by the method now under consideration, for 
if this be so then (i) the chief lines and dutings of sodium 
should be seen in the dame itself, and ( 2 ) the spark should 
pass through the vapor after complete volatilization has 
been effected without any visible effect. 
Observation and experiment have largely confirmed these 
predictions. Using two prisms of 6o° and a high-power 
eyepiece to enfeeble the continuous spectrum of the densest 
vapor produced at a high temperature , the green lines, the 
dutings recorded by Roscoe and Schuster, and another 
coarser system of dutings, so far as I know not yet de- 
scribed, are beautirully seen. I say largely, and not com- 
pletely, because the double red line and the lines in the 
blue have not yet been seen'in the dame, either with one, 
two, or four prisms of 6o°, though the lines are seen during 
volatilization if a spark be passed through the dame. Sub- 
sequent inquiry may perhaps show that this is due to the 
sharp boundary of the heated region, and to the fact that 
j lines in question represent the vibrations of molecular 
