82 PROFESSOR J. N. LOCKYER ON THE PHOTOGRAPHIC 
(a) The Complex Origin of the Spectra of the Nebule. 
As pointed out in the paper referred to, the bright lines should have three origins, 
namely :— 
(1) Non-condensable gases driven out of the meteorites. 
(2) Low temperature vapours produced by a large number of feeble collisions. 
(8) High temperature vapours produced by a small number of end-on collisions. 
It will be seen from the tables that the requirements of the hypothesis in this 
respect are fully satisfied. 
The lines of hydrogen and the flutings of carbon are what we should expect from 
the large interspaces ; the flutings of magnesium and the low temperature lines of 
iron and calcium bring us face to face with phenomena connected with low tempera- 
tures, and they may be ascribed to the partial collisions ; while the lines coincident 
with chromospheric lines must be regarded as high temperature products, since the 
solar chromosphere may be taken as indicating the spectrum we might expect to be 
associated with the high temperature vapours produced by the end-on collisions. 
The undoubted presence of the lines D, and \4471 left but little doubt as to the 
chromospheric relationship of some of the lines in the nebular spectrum, but the flood 
of new light thrown by the photographs taken with the prismatic cameras during the 
total eclipse of the sun on April 16th, 1893, put the matter beyond all question. 
The discussion of the eclipse photographs will form the subject of a separate 
communication, but it may be here stated that the spectrum of the nebula shows a 
number of coincidences with lines seen in the spectrum of the chromosphere and 
prominences. 
(b) The Passage to the Bright-Line Stars. 
The association of the nebulee with the bright-line stars in the classification of the 
heavenly bodies was, I think, first suggested by me in 1887.* 
So far as the planetary nebulee are concerned, this grouping has been abundantly 
confirmed by Professor Pickrrine’s work on the bright-line stars, and by the visual 
observations of Professor KEELER. 
Professor PrcKERINGt tabulates the lines, and concludes with the statement that, 
“Owing to the similarity of the spectra of the planetary nebulee and the bright-line 
stars, they may be conveniently united in a fifth type.” It is clear then, that in this 
particular, Professor PrcKERING accepts my proposed classification. 
Mr. KEELER writes,{ ‘‘ The spectra of the nuclei of the planetary nebule have a 
remarkable resemblance to the Wotr-Raver and other bright-line stars, and an 
* © Roy. Soe. Proc.,’ vol. 43, p. 144. 
+ ‘Ast. Nach.,’ 3025, 1891. 
t ‘ Proc, Ast. Soc. Pacific,’ vol. 2, No. 11, Nov. 29, 1890. 
