The other elements are:—
| Deimos. | Phobos. | |
| Mean long. 1894, Oct. o.o G.M.T | 186.25° | 296.13° |
| Mean daily motion (tropical) | 285.16198° | 1128.84396° |
| Mean distance (Δ = 1) | 32.373″ | 12.938″ |
| Long. of pericentre, (π + N) | 264° + 6.375°t | 14° + 158.0°t |
| Eccentricity of orbit | 0.0031 | 0.0217 |
| Epoch for t | 1900.0 | 1900.0 |
Bibliography.—Flammarion, La Planète Mars et ses conditions d’habitilité (Paris, 1892), embodies so copious a résumé of all the publications and drawings relating to Mars up to 1891 that there is little occasion for reference in detail to early publications. Among the principal sources may be mentioned the Monthly Notices and Memoirs of the Royal Astronomical Society, the publications of the Astronomical Society of the Pacific, especially vols. vi., viii. and ix., containing observations and discussions by the Mt Hamilton astronomers, and the journals, Sidereal Messenger, Astronomy and Astrophysics and Astrophysical Journal. Schiaparelli’s extended memoirs appeared under the general title Osservazioni astronomiche e fisiche sull’ asse di rotazione e sulla topografia del pianeta Marte, and were published in different volumes of the Memoirs of the Reale Accademia dei Lincei of Rome. The observations and drawings of Lowell are found in extenso in Annals of the Lowell Observatory. Lowell’s conclusions are summarized in Mars and its Canals, by Percival Lowell (1906), and Mars as the Abode of Life (1909). In connexion with his work may be mentioned Mars and its Mystery, by Edward S. Morse (Boston, 1906), the work of a naturalist who made studies of the planet at the Lowell Observatory in 1905. Brief discussions and notices will also be found in the Lowell Observatory Bulletins. The optical principles involved in the interpretations of the canals are discussed in recent volumes of the Monthly Notices, R.A.S., and in the Astrophysical Journal. In 1907 the veteran A. R. Wallace disputed Lowell’s views vigorously in his Is Mars Habitable? and was briefly answered by Lowell in Nature, who contended that Wallace’s theory was not in accord with celestial mechanics.
(S. N.)
[1] Astronomy and Astrophysics, iii. 752, and Astron. Soc. of the Pacific, Publications, vi. 273 and ix. 109.
[2] According to Percival Lowell these results were, however, inconclusive because the strong atmospheric lines lie redwards beyond the part of the spectrum then possible to observe. Subsequently, by experimenting with sensitizing dyes, Dr Slipher of the Lowell Observatory succeeded in 1908 in photographing the spectrum far into the red. Comparison spectrograms of Mars and the Moon, taken by him at equal altitudes on such plates, eight in all, show the “a” band, the great band of water-vapour was distinctly stronger in the spectrum of Mars, thus affording what appeared decisive evidence of water vapour in the atmosphere of the planet.
[3] Lowell, Mars and its Canals, p. 101.
[4] Phil. Trans., vol. 202 A, p. 525.
[5] Proc. Amer. Acad. Arts and Sciences, vol. xlii. No. 25.