Additional Table of compared spectra.
As an addendum to the foregoing, on Plate IX. fig. 1 will be found a Table I have prepared, in which a type Aurora and also Vogel’s and Barker’s Auroræ are compared with eight other spectra, viz.:—
| S. | Solar spectrum. |
| N. | Nitrogen (air): Watts. |
| O. | Oxygen (air): Watts. |
| C.H. | Carburetted-hydrogen vacuum-tube: Watts. |
| C.I. | Carburetted-hydrogen flame: Watts. |
| C.C. | Blue base of candle-flame: Capron. |
| O.P. | Oxygen vacuum-tube: Procter. |
| I. | Iron: Watts. |
The divisions and vertical lines will guide the eye in making comparison of the spectra.
CHAPTER XII.
SOME NOTES ON PROFESSOR ÅNGSTRÖM’S THEORY OF THE AURORA-SPECTRUM.
[The substance of these appeared in the ‘Philosophical Magazine’ for April 1875, in conjunction with the “Comparison of the Tube and other Spectra” (Chapter XI.), but they are now, for the sake of convenience, made a separate article.]
Professor Ångström’s propositions.
In a contribution by the late Professor Ångström to a solution of the problem of the Aurora-spectrum (an abstract of which appeared in ‘Nature’ of July 16, 1874), the Professor is stated, amongst other things, to have laid down certain propositions in substance as follows:—