306 J. N. Lockyer—New Method of Spectrum Observation. 
than those which give us the yellow and green lines. The vis- 
ibility of the green lines, which are short, in the flame, taken in 
connection with the fact that they have been seen alone ina vac- 
uum tube, is enough for my present purpose. 
With regard to the second point, the passage from the heat- 
horizon of the flame to that of the spark, after volatilization is 
complete, produces no visible effect, indicating that in all proba- 
bility the effects heretofore ascribed to quantity have been due 
to the presence of the molecular groupings of greater complex- 
ity. The more there is to dissociate, the more time is required to 
run through the series, and the better the first stages are seen. 
et us now turn to lithium. 
Seeing that the red line is absent while the violet lithium 
line is strong among the Fraunhofer lines, we may imagine that 
the flame has not done the work of dissociation in the case of 
lithium as completely as the sun does it, so that (1) the other 
lines of lithium should not be visible, even with the new pre- 
cautions, in the flame spectrum, and (2) a passage from the 
heat-level of the flame to that of the spark after volatilization 
should produce the other lines which we know to exist in the 
spectrum of the metal in the orange, blue and violet. 
Experiment and observation have also confirmed this result, 
so far as the yellow and blue lines go; that in the violet 18 
difficult of observation.* 
We next come to potassium. 
The potassium lines usually recorded as not seen ina flame, 
but which are observed with a spark, are not very brilliant; 
nor are they strong among the Fraunhofer lines. Seeing, 
therefore, that a high temperature does not greatly sprites 
them, we may expect to find them in the flame. They are a> 
most all there when they are looked for with proper precautions, 
but those in all probability present inthe sun are brightened 
on passing the spark, showing apparently that the flame vola- 
cine with some difficulty the molecule which gives the line ™ 
the red. 
The flame spectrum of magnesium perhaps presents us best 
* The way in which the lines in the flame are unaffected by the spark strikingly 
reminds me of the following remarks of Angstrém and Thalén: “ The Fraunhofer 
D er by no 
marked either as to form or color. These two different kinds of lines are, a3 ea 
iron; and those which remain, after the iron-lines are abstracted, 
other metals; calcium, ese, chromium, ete.”—(‘ Angstrom and Thalén 08 
the Fraunhofer Lines, together with a Diagram of the Violet Part o 
Spectrum.” Upsala, 1866, p. 6.) 
