be 8 od 
II. On the Photographic Spectrum of the Great Nebula in Orion. 
By J. Norman Lockyer, C.B., F.R.S. 
Received June 13,—Read June 21, 1894. 
CoNnTENTS. 
PAGE. 
ee Descriptionofabheyphovoora ph sire waren wemr teria enn y ar iierie es i sunny ar lnton Dairies ((3 
leptablerotwaveclensthse mote. ce sack mb ater Meh ty hase ae ee Rec a eel 
III. The origins of the lines recorded . . . . . AD lauperee SSMaL tint mig fensse | ies eet cm CDH Lf 
IV. The variation of the spectrum in ‘different regions 1 themebul ae wee seca eet Seed S 
Y. Discussion of the results in relation to the meteoritic hypothesis . . ...... 81 
(a) The complex origin of the spectra of nebule . . .......2,.7 ~. «282 
(b) The passage to bright-line stars . . cot Nap einsitae: Wana aoe ica rot enmea eee fara aittoy™ 
(c) Relation to stars of Groups II. and III. Ne eaienebi lly iets ess sila Orisa ee leon ota) 
WeleeGeneraliconclusionsi, PRVIths, otk cheat eats hc ae Meet aINaR a teenth Sem riage “EAERA Synet neta, SQ)T! 
J. DESCRIPTION OF THE PHOTOGRAPHS. 
Iv February, 1890, I communicated to the Royal Society a preliminary note on some 
photographs of the spectrum of the Orion Nebula, taken at Westgate-on-Sea.* 
The detailed discussion of the photographs has been reserved with the hope of 
securing others, but owing to other pressing work no further photographs have been 
obtained. 
As the photographs in question show a greater number of lines than others which 
have been described, and especially as they appear to have an important bearing on 
the study of certain types of stellar spectra, I have thought it desirable that the 
publication of the results should no longer be delayed. 
The instrument employed was the thirty-inch reflector, and a spectroscope by 
Hineer, having one prism of 60° and two half-prisms of 30°. 
Mawson’s instantaneous plates were used. The exposures were carried up to four 
hours, and five photographs were taken, some of them with shorter exposures than 
that named, in consequence of the sky becoming clouded or irregularities in the driving 
* «Roy. Soc. Proc.,’ vol. 48, p. 199. 
MDCCCXCV.—A, L 5 3.95 
