[1] ??????, a hollow.

[2] p????, a cask.

[3] ??s?, a chasm.

[4] M. LemstrÖm (Swedish Expedition, 1868) concludes that the corona of the Aurora Borealis is not entirely a phenomenon of perspective, but that the rays have a true curvature, that they are currents flowing in the same direction and attract each other. There is also an account [antÈ, p. 16] of an Aurora at Melville Island (Parry’s first voyage), in which two arches were seen curving towards each other.

[5] A brilliant display in December 1870, on the east coast of Sicily, was followed by very violent storms, with the overflow of the Tiber and the flooding of Rome.

[6] Some curious instances have been recently (January 1879) given in the ‘Times’ of such electric phenomena, comprising, amongst others, gas lighted by the finger in Canada, points of flame seen on the ironwork of Teignmouth Bridge, and similar points seen on the alpenstocks and axes of a party making a mountain ascent in Switzerland.

[7] On the occasion of the Aurora of September 24, 1870, Dr. Allnatt says, “the air seemed literally alive with the unwonted phosphorescence.”

[8] See, however, Dr. Schuster’s article “On the Spectra of Lightning,” Phil. Mag. May 1879, p. 316.

[9] The proof from occulted stars merely goes to the fact that the moon possesses no atmosphere appreciable in that way. It may still be a question whether there does not exist something of the kind, lying low and close to the surface, and possibly of a rarefied character, which would scarcely make itself visible by its effects in occultations. Cloud-vapour might form in an atmosphere of inconsiderable density.

[10] This observation is not without a certain amount of confirmation by more recent ones, in which certain lunar objects and regions have been suspected of mist or vapour. Mr. Birt (‘English Mechanic,’ vol. xxviii. no. 725) mentions two—the cloud-like appearance of the white patch west of Picard, and the interior of Tycho, which at one time always misty and ill-defined, is now become perfectly distinct and sharply defined.

December 4, 1878, 4h 45m. I observed Klein’s crater as a dull dark spot, larger than the true object; and while definition was good and other objects were well defined, “the floor of Klein’s object, the oval spot near, and also Agrippa (especially), all had an odd misty look as if vapour were in or about them” (‘English Mechanic,’ vol. xxviii. no. 727). The mystery of different observers seeing and not seeing Klein’s object on the same night is hardly to be accounted for by the angle of illumination.

[11] Some doubt has been cast on this observation, on the ground that nothing unusual was seen, and that the appearances were only those ordinarily presented by the moon at its then phase. I simply give the account as it appears in the scientific journal in which it was published.

[12] The question of a connexion between the waxing and waning of the solar corona and the prevalence of sun-spots is now being mooted, and may have an important bearing on the subject of the constitution of the corona. It would seem that when the corona has been examined about the time of minimum of sun-spots, it has proved fainter though more extended, while the bright lines of the spectrum have been absent, indicating a change or variance in the gaseous part of it at those periods.

[13] There seems to be some confusion as to the W.L. here given; 5567 is usually accepted as ÅngstrÖm’s line, while Prof. Smyth refers to it as 5579. The position, too, when examined with a spectroscope of greater dispersion, is not exactly over the citron-line of acetylene, both the above referred to lines lying somewhat more towards the violet end of the spectrum (see Plate V. fig. 7).

[14] ÅngstrÖm’s drawing, in giving this character to the two Aurora-bands which are said to correspond with violet-pole bands about 47 and 43, is incorrect, and calculated to mislead by giving the Aurora-bands a feature corresponding to the violet-pole bands which they do not possess. I am not aware of any Aurora-line or band which is described as distinguished by degrading towards the violet.

[15] The tubes generally seem marked Si Fl instead of the ordinary notation Si F. Si Fl6 is probably, in fact, Si F4.

[16] Dr. Schuster has found that while the line-spectrum of lightning is attributable to N, it has also a band-spectrum, which he considers due to O and a slight trace of CO2 (Phil. Mag. 5th ser. vol. vii. p. 321).

[17] In these observations some suggestions made by Mr. Capron have been incorporated.

[This was Mr. Lockyer’s note. In point of fact, the Author was responsible for the verbatim paragraphs comprised between the letters A and B, and C and D, in the instructions as now reprinted.]

[18] Communicated by the author to the Royal Saxon Academy of Science, 1871.

[19] Reports of the Royal Saxon Academy of Science, Oct. 31, 1871.

[20] This red line was first noticed by ZÖllner.

[21] Recherches sur le Spectre Solaire, p. 42.

[22] American Journal of Science, lxviii. 123.