The next morning the solar lines were verified in sunlight. I subjoin (Plate XI. fig. 3) copies of the two spectra as printed in ‘Nature,’ the auroral lines being marked A, the solar lines by the usual designating letters, and the carbon by _Car_. To these spectra I have added for comparison Dr. Vogel’s spectrum of the Aurora Borealis. Captain Maclear could not account for the different positions of the auroral lines in the two plates; for the prism, as far as he was aware, was not moved during the observations. As the solar lines are indicated in the same place in both spectra, the case would seem one of actual change of position of the auroral lines during observation. A comparison of the two spectra gives the impression that the lower one is the same as the upper, except that the dispersion is greater, the lines remaining relatively in position. One does not, however, see how the dispersion could have so varied in a single-prism instrument, and the position of the solar lines is adverse to such an explanation. There is a suspicion that Auroræ are not always identical in position of some of the lines; but the line in the green (considerably out of place in the lower Australis spectrum) has always, within small limits, the same position. It will be noticed how much further the Australis spectrum runs into the violet than Vogel’s Borealis, the latter having no lines much beyond F. The faint line (No. 2) mentioned by Captain Maclear possibly corresponds with Dr. Vogel’s band. The absence of the four lines of the Aurora Borealis in the green part of the spectrum of the Australis is peculiar; and in this respect, too, the two Australis spectra agree. [Sidenote: Comparison of the lines.] The nearest approaches to Captain Maclear’s lines (of the upper spectrum) which I can find are:— Line Corresponding line. 1. 5567, Ångström. 2. (The faint line.) Vogel’s band, 4694-4629. 3. I find no approximately corresponding line. 4. 4350, Alvan Clarke. But the comparisons are not by any means close. Further observations of the Australis spectrum are very desirable. _Prof. Piazzi Smyth’s Aurora-Spectra._ [Sidenote: Prof. Piazzi Smyth’s chemical and auroral spectra.] Prof. Piazzi Smyth, in volume xiv. of the ‘Edinburgh Astronomical Observations,’ 1870-77, has compared simultaneously the Aurora-spectrum with the sets of bright lines seen in the blue base of flame—the lines of potassium, lithium, sodium, thallium, and indium being also introduced for comparison. The spectra are drawn as seen under small dispersion, and will prove most useful in cases where an Aurora is not bright enough to admit of the lines being measured by micrometer, and the eye and comparison spectrum are obliged to be resorted to. [Illustration: Plate XII.] _Author’s Catalogue of the Auroral Lines._ (See Plate XII.)