130 HISTORY OF THE [1860-70 We see greatly increased activity in the observation of meteors and meteor radiants, and also the establishment of the identity of orbits of certain comets and meteors. We see great advances in the determination of the solar parallax, great advances in planetary theory, and great advances in lunar theory. We see the development of the idea that the lunar acceleration must be connected with tidal friction and the consequent lengthen- ing of the day. We see the figure of the earth defined in terms of a possible ellipsoid. We see the number of minor planets carried well beyond the first century, the hundredth being named after that goddess of mischief, Hecate. We see the completion of Argelander's Bonn Durchmusterung, and the publication of the following notable contributions : Sir John Herschel's General Catalogue 0/5079 Nebulce (1864). Lassell's (Marth's) Catalogue 0/600 New Nebulce (1867). Rosse's Observations of Nebulce with his 6-foot Speculum (1861). Carrington's Memoir on Sun Spots (1863). De la Rue's Memoir on the Solar Eclipse, 1860 July 18 (1862). Tennant's Memoir on the Solar Eclipse, 1868 August 17-18 (1869). De la Rue and Balfour Stewart's Heliographic Positions and Areas of Sun Spots (1862). Huggins and Miller's work on The Spectra of the Stars and Nebulse (1864). Dunkin's Memoir on the Motion of the Sun in Space (1864). Lockyer's early work in Solar Physics (1868). Huggins's Memoir on his Attempt to determine whether Stars are moving towards or from the Earth (1868). Bond's monograph on Donati's Comet (1862). Thomson's paper on The Rigidity of the Earth (1863). Airy 's work on The Diurnal Variation of Magnetic Elements. Chauvenet's Spherical and Practical Astronomy (1863). Watson's Theoretical Astronomy (1868). The decade was notable, too, for several remarkable astronomical events. The earth passed through the tail of a comet (1861). The star T Coronae blazed out with great brilliance (1866 May). The long-expected November meteors made their memorable display (1866). There were two solar eclipses which have become historically notable : 1860 July 18, and 1868 August 17-18.
