810 J. N. Lockyer—New Method of Spectrum Observation. 
was found by comparison with the solar spectrum, to be at 
w.]. 4570 3, and coincident with no Fraunhofer line. The 
passage of the spark abolished this line, at the same time 
bringing in the two lines given by Thalén at w.l, 4481°0 and 
47035, both of which are reversed in the solar spectrum. 
o line was seen at Thalén’s w.1. 4586 5, the nearest approach 
to which was the line seen at the temperature of the Bunsen 
flame at w.|. 4570°3, a difference of.more than sixteen divisions . 
of the scale. 
I am now preparing maps showing the phenomena observed 
at various heat-levels. I think it is not too much to hope that 
a careful study of such maps, showing the results already 
obtained or to be obtained, at varying temperatures, controlled 
by observation of the condition under which changes are 
brought about, will, if we accept the idea that various dissocia- 
tions of the molecules present in the solid are brought about 
by different stages of heat, and then reverse the process, enable 
us to determine the mode of evolution by which the molecules 
vibrating in the atmospheres of the hottest stars associate into 
those of which the solid metal is composed. I put this sugges- 
tion forward with the greater confidence, because I see that 
help can be got from various converging lines of work. To 
some of these I may briefly allude here :— 
1. We have the lines present in the solar spectrum and 
absent from it. : 
Example.—The red potassium line present in the flame 1s 
absent from the sun; some of the other lines are present. 
ave the varying thicknesses of the lines of any one 
element in the sun to compare with the thicknesses produced 
at different temperatures in the laboratory. 
Ezxample.—The various lines of magnesium, notably b, the 
most refrangible line given by Thalén and the other blue line. 
8. We have the remarkable behavior of metals vaporized 10 
a vacuum at the lowest temperatures. : 
tzample.—Sodium gives us D, potassium gives us the triplet 
in the green-yellow; calcium gives us the line in the blue; 
thus separating those lines from all the others of those metals. 
e have the remarkable behavior of the same vapors UD 
der like circumstances, the temperature alone being changed ; 
when this is increased lines visible under ordinary conditions 
are brought in, and are seen in different parts of the tube, 8° 
that each line in turn (and therefore, I presume, each molecule 
which produces it) is separated from those with which it '§ 
generally seen in company. 
ample.—By increasing the temperature we get the green 
line of sodium without D, and some of the magnesium lines 
have been seen separated from the others. 
