R. Meldola— Bright Lines in the Solar Spectrum. 295 
examined immediately after its emergence from this layer, the 
oxygen (and nitrogen) lines would appear dark, but less con- 
spicuous than the metallic lines, for reasons which will be entered 
into later on in this paper.* After traversing the chromosphere 
the ray reaches the zone of combustion, in which region, owing 
to the increased temperature, the lines of all elements which 
extend so far would tend to be reversed into bright lines of 
radiation. 
I say “tend to be reversed,” because whether they would 
actually become so depends upon the specific absorptive power 
of the elements concerned for the rays in question. Thus, let 
there be two gases, A and B, of which the spectral lines are 
by dark lines, Aa, Ag, Ay, Ba, Bg and By, of which the first 
maj to give the “com 
of this gas (Nature, vol. xvii, p. 148). The recent observations of Lockyer upon 
the calcium spectrum (Proc. Roy. Soc., xxiv, 352) tend to show that the tem- 
of this layer is intermediate in dissociation power between that produced 
senate believe would produce a state of molecular dissociation corresponding to 
t It i ble that the te ture of the ch h fall off at some 
+t 1s possible that the temperature of the chromosphere may f 
Particular level, so gi ap ve such boundary the “compound” oxygen 
Spectrum. Should this he the case, the higher portion of the chromosphere may 
obviously be left out of consideration, so far as relates to its absorbing action on 
the line spectrum 
oxygen. 
Am. Jour. Sct.—Tuirp — Vou. XVI, No. 94.—Oor., 1878, 
1 
