SPECTRA OF SOME OF THE BRIGHTER STARS. 
713 
high temperature spectra of the various chemical elements, showing many 
more lines. The difference between these and the lines seen in stars of 
increasing temperature should be one due to tbe different percentage com¬ 
position of the absorbing layers, so far as the known lines are concerned. 
With this increasing line absorption there will be a recurrence of the continuous 
absorption in the ultra-violet. 
(Stage 3).—With the further thinning of the hydrogen lines and reduction of 
temperature of the atmosphere, the absorption flutings of the compounds of 
carbon should come in. 
So much, then, for what we should expect, assuming the hypothesis to be true. 
I now proceed to show how far these requirements are satisfied by the mass of new 
facts now at our disposal. 
(2.) The Actual Phenomena Recorded on the Photographs. 
Nebulce. 
A preliminary account of the photographs of the spectrum of the Orion Nebula 
taken with Instrument E has already been published,* and though the discussion is 
not yet completed, it may be stated that the lines recorded in the spectrum are at 
wave-lengths which approximate very closely to the lines of hydrogen, to flutings 
which appear in the spectra of compounds of carbon, to a fluting of magnesium at 
5006, and to the longest flame lines of iron, calcium, and magnesium. 
The chromospheric line designated Dg has been recorded in the visual spectrum of 
the Orion Nebula by Dr. Copeland,! and the observation has since been confirmed 
by Mr. Taylor. J 
The line which is always associated with Dg in the spectrum of the chromosphere, 
viz., that at X4471 (Lorenzoni’s f), is also shown in the photograph of the spectrum 
of the Orion Nebula. 
The requirements of the hypothesis with regard to nebulae are therefore met in 
every point so far considered by the new facts. 
Dividing up the lines into the three groups of origins suggested, we have in the 
case of the Orion Nebula ; — 
(a.) Spectrum of large interspace (= that 
of non-condensable gases driven out of 
the meteorites) 
Lines of hydrogen ; flutings 
of carbon. 
* ‘ Roy. Soc. Proc.,’ yol. 48, p. 199. 
t ‘]\[oiathly Notices,’ vol. 48, p. .360. 
t Ibid., vol. 49, p. 124. 
4 Y 
MDCCCXCITT.— A, 
