714 
PROFESSOR J. N. LOCKTER ON THE PHOTOGRAPHIC 
r Fluting of magnesium at 
{h.) Spectrum of vapours produced by the 1 _ y 5006 low temperature, 
large number of partial collisions | “ of iron, calcium, and 
magnesium.+ 
(e.) Spectrum of the vapours produced 
at a very high temperature by the 
relatively small number of end-on 
collisions. The solar chromosphere }■ = 
may he taken as indicating the spec¬ 
trum associated witli tliis very high 
temperature 
A detailed reference to those nebulae showing the spectra of carbon bands alone is 
reserved for a future communication. 
Chromospheric lines, 
Dg -f \ 4471. 
Bright-Line Stars. 
Professor Pickering has shown that the Draper Memorial Photographs (copies 
of which he lias very kindly forwarded me) prove that brightdine stars are 
intimately connected with the planetary nebulae, the lines in the spectra being 
almost identical, as the following table will show :—| 
* Mj suggestion of the coincidence of the brightest line of the nebular spectrum with the fluting of 
magnesium at X ,5006’5, has given rise to discussion, and some observations have been made bj Professor 
Keeler, with the three-foot Lick refractor and the third order spectrum of a diffraction grating, on this 
subject. When I first suggested magnesium as the origin of the chief line in the nebular spectrum, the 
measurements then available were quite sufficient to justify it as regards position, and there were other 
and. stronger grounds for the suggestion, depending u^ion laboratory experiments and upon the 
frequently observed fluted character of the line. There are so many pitfalls attending the delicate 
measurements involved in such an inquiry, that I am not yet convinced that the absolute wave-length 
of the nebular line has been determined. The Astronomer-Royal has recently pointed out (‘Monthly 
Notices,’ vol. 62, p. 245) that the varying flexure of the telescope, when presented to different parts of 
the sky, has an effect on the measurements, and in the spectroscopic determinations of the motions of 
the stars in the line of sight at Greenwich, the displacement of the lines in the spectrum of a star was 
found to give clear indications of the existence of the systematic error referred to. Further, I have 
convinced myself of the fluted nature of the line by new observations made with instruments best fitted 
to show it, while the Lick telescope is perhaps the ideal telescope not to employ in such an inquiiy. 
Hence, although the visibility of magnesium in nebulae is not fundamental for my argument, I still 
hold that it is more probably the origin of the nebular line than an unknown form of nitrogen. 
t I have previously given evidence deduced from eye observations, indicating the presence of other low 
temperature flutings of manganese and magnesium, 
j; ‘ Ast. Nach.,’ No. 3025, p. L 
