G. F. Barker’s observations.
George F. Barker, observing at New Haven (U.S.A.), saw, on November 9th, a crimson and white Aurora, which he examined with a single glass-prism spectroscope, by Duboscq, of Paris. The line positions were obtained by an illuminated millimetre scale. In the white Aurora were four lines (the red one being absent); in the red Aurora five. The wave-lengths of the Aurora-lines were run out as follows:—
- (1.) Between C and D, 6230 (Zöllner’s 6270).
- (2.) ” D and E, 5620 (Ångström’s 5570).
- (3.) ” E and b, 5170 (Winlock’s 5200).
- (4.) ” b and F, 5020.
- (5.) ” F and G, 4820 (Alvan Clarke’s, jun., 4850).
Spectrum of Aurora of Feb. 4, 1872. Prof. Piazzi Smyth’s observations.
Mr. Procter’s Aurora-lines will be found noticed in connexion with the spectrum of oxygen; and Lord Lindsay’s lines, with a comparison scale drawing, are separately described further on in this Chapter. The Aurora of February 4th, 1872, had many observers; some of whom communicated at the time spectroscopic notes. Professor Piazzi Smyth minutely describes the display as seen in Edinburgh, and saw “Ångström’s green Aurora-line perpetually over citron acetylene[13] at W.L. 5579, and the red Aurora-line between lithium a and sodium a, but nearer to the latter, say at W.L. 6370.” Extremely faint greenish and bluish lines also appeared at W.L. 5300, 5100, and 4900 nearly.
Rev. T. W. Webb’s observations.
The Rev. T. W. Webb, with a very fine slit, saw the green Auroral line even in the light reflected from white paper. With a wider slit he saw a crimson band in the brighter patches of that hue, and beyond an extent of greenish or bluish light, which he suspected to be composed of contiguous bands.
R. J. Friswell’s observations.
R. J. Friswell, coming up the Channel at 9.40, with a Hoffman’s direct-vision spectroscope (the observing telescope removed), saw the green line, a crimson line near C, and faint traces of structure in the blue and violet.