+-----+--------+------------------------------------------------+ |W.L. |Probable| Remarks. | | | error. | | +-----+--------+------------------------------------------------+ |6297 | 14 |Very bright stripe. } | | | | } | |5569 | 2 |Brightest line of the spectrum, } | | | | became noticeably fainter at } On a faintly | | | | appearance of the red line. } lighted | | | | } ground. | |5390 | .. |Extremely faint line; } | | | | unreliable observation. } | | | | } | |5233 | 4 |Moderately bright. } | | | | | |5189 | 9 |This line was very bright when the red line | | | | appeared at the same time; otherwise equal | | | | in brilliancy with the preceding one. | | | | | |5004 | 3 |Very bright line. | | | | | |4694}| |{Broad band of light, somewhat less brilliant | |4663}| 3 |{ in the middle; very faint in those parts of | |4629}| |{ the Aurora in which the red line appeared. | +-----+--------+------------------------------------------------+ A translation of Dr. Vogel’s interesting paper will be found printed _in extenso_ in Appendix E, and his lithographed drawings of the spectrum in the green and red portions of the Aurora respectively on Plate VI. figs. 2 and 3. The observations of April 9th by Dr. Vogel are probably, up to the present time, the most exact of any one Aurora, and I have therefore in most cases used them for comparison. [Sidenote: Mr. Backhouse’s catalogue of lines.] Mr. Backhouse, in a letter to ‘Nature,’ commenting upon my catalogue of lines, gave the following as the latest determinations from his own observations:— No. 1. Wave-length 6060 2. ” 5660 3. ” 5165 4. ” 5015 6. ” 4625 7. ” 4305 (6060 must be a mistake for 6260, and 5660 for 5560.—J. R. C.) Mr. Backhouse never saw a line at 5320 again. He found the continuous spectrum to reach from No. 2 to No. 7, being brightest from a little beyond No. 2 to No. 6. This part of the spectrum did not give him so much the idea of a true “continuous spectrum” as of a series of bright bands too close to be distinguished. [Sidenote: Subsequent full catalogue of Auroral lines.]