[Footnote 243: "Sicut bombyces filo fundendo, sic cometas cauda
exspiranda consumi et denique mori."--_De Cometis_, Op., vol. vii., p.
110.]

[Footnote 244: Considerable uncertainty, however, still prevails on the
point. The inverse relation assumed by Lagrange to exist between
distance from the sun and density brought out the Mercurian mass
1/2025810 that of the sun (Laplace, _Exposition du Syst. du Monde_, t.
ii., p. 50, ed. 1824). Von Asten deduced from the movements of Encke's
comet, 1818-48, a value of 1/7636440; while Backlund from its seven
returns, 1871-1891, derived 1/9647000 (_Comptes Rendus_, Oct. 1, 1894).]

[Footnote 245: Arago, _Annuaire_ (1832), p. 218.]

[Footnote 246: Hind, _The Comets_, p. 20.]

[Footnote 247: _Phil. Trans._, vol. xlvi., p. 204.]

[Footnote 248: _Astr. Nach._, No. 2,134.]

[Footnote 249: _Comptes Rendus_, t. cvii., p. 588.]

[Footnote 250: _Mem. de St. Petersbourg_, t. xxxii., No. 3, 1884; _Astr.
Nach._, No. 2,727.]

[Footnote 251: _Month. Not._, vol. xix., p. 72.]

[Footnote 252: _Mecanique Celeste_, t. ii., p. 197.]

[Footnote 253: See Berberich, _Astr. Nach._, Nos. 2,836-7, 3,125;
Deichmueller, _Ibid._, No. 3,123.]

[Footnote 254: _Month. Not._, vol. ii., p. 117.]

[Footnote 255: _Astr. Nach._, No. 128.]

[Footnote 256: _Annuaire_, 1832, p. 186.]

[Footnote 257: _Am. Journ. of Science_, vol. i. (2nd series), p. 293.
Prof. Hubbard's calculations indicated a probability that the definitive
separation of the two nuclei occurred as early as September 30, 1884.
_Astronomical Journal_ (Gould's), vol. iv., p. 5. See also, on the
subject of this comet, W. T. Lynn, _Intellectual Observer_, vol. xi., p.
208; E. Ledger, _Observatory_, August, 1883, p. 244; and H. A. Newton,
_Am. Journ. of Science_, vol. xxxi., p. 81, February, 1886.]

[Footnote 258: _Month. Not._, vol. vii., p. 73.]

[Footnote 259: _Bulletin Ac. Imp. de St. Petersbourg_, t. vi., col. 77.
The latest observation of the parent nucleus was that of Argelander,
April 27, at Bonn.]

[Footnote 260: D'Arrest, _Astr. Nach._, No. 1,624.]

[Footnote 261: _Der Brorsen'sche Comet._ Von Dr. E. Lamp, Kiel, 1892;
Plummer, _Knowledge_, vol. xix., p. 41.]

[Footnote 262: Schulhof, _Astr. Nach._, No. 3,267; _Observatory_, vol.
xviii., p. 64; F. H. Seares, _Astr. Nach._, Nos. 3,606-7; Plummer,
_Knowledge_, vol. xix., p. 156.]

[Footnote 263: _Comptes Rendus_, t. xxv., p. 570.]

[Footnote 264: _Month. Not._, vol. xii., p.