t. ii., p. 27; _Astr. Nach._, No. 2,021;
_Am. Jour. of Sc._, vol. xxv., p. 430.]

[Footnote 872: _Mem. Spettr. Ital._, Dicembre, 1882; _Am. Jour. of Sc._,
vol. xxv., p. 328.]

[Footnote 873: _Comptes Rendus_, t. cxvi., p. 288.]

[Footnote 874: Vogel, _Spectra der Planeten_, p. 15.]

[Footnote 875: _Nature_, vol. xix., p. 23.]

[Footnote 876: _Nova Acta Acad. Naturae Curiosorum_, Bd. x., 239.]

[Footnote 877: _Astr. Jahrbuch_, 1809, p. 164.]

[Footnote 878: _Month Not._, vol. xliii., p. 331.]

[Footnote 879: _Report Brit. Ass._, 1873, p. 407. The paper contains a
valuable record of observations of the phenomenon.]

[Footnote 880: _Photom. Untersuchungen_, p. 301.]

[Footnote 881: _Bothkamp Beobachtungen_, Heft ii., p. 126.]

[Footnote 882: _Astr. Nach._, No. 2,818.]

[Footnote 883: _Memoires de l'Acad. de Bruxelles_, t. xlix., No. 5, 4to;
_Astr. Nach._, No. 2,809; _f._ Schorr, _Der Venusmond_, 1875.]

[Footnote 884: _Phil. Trans._, 1839, 1841, 1842.]

[Footnote 885: Delaunay objected (_Comptes Rendus_, t. lxvii., p. 65)
that the viscosity of the contained liquid (of which Hopkins took no
account) would, where the movements were so excessively slow as those of
the earth's axis, almost certainly cause it to behave like a solid. Lord
Kelvin, however (_Report Brit. Ass._, 1876, ii., p. 1), considered
Hopkins's argument valid as regards the comparatively quick solar
semi-annual and lunar fortnightly nutations.]

[Footnote 886: _Phil. Trans._, cliii., p. 573.]

[Footnote 887: _Report Brit. Ass._, 1868, p. 494.]

[Footnote 888: _Ibid._, 1882, p. 474.]

[Footnote 889: Albrecht, _Astr. Nach._, No. 3,131.]

[Footnote 890: _Astr. Jour._, Nos. 248, 249.]

[Footnote 891: _Ibid._, No. 258.]

[Footnote 892: _Month. Not._, vol. lii., p. 336.]

[Footnote 893: _Astr. Nach._, No. 3,097; _Phil. Trans._, vol. clxxxvi.,
A., p. 469; _Proc. Roy. Soc._, vol. lix.]

[Footnote 894: See Chandler's searching investigations, _Astr. Jour._,
Nos. 329, 344, 351, 392, 402, 406, 412, 446, 489, 490, 494, 495.]

[Footnote 895: Rees, _Pop. Astr._, No. 74, 1900.]

[Footnote 896: _Nature_, vol. lxi., p. 447; see also A. V. Baecklund,
_Astr. Nach._, No. 3,787.]

[Footnote 897: _Trans. Geol. Soc._, vol. iii. (2d ser.), p. 293.]

[Footnote 898: See his _Treatise on Astronomy_, p. 199 (1833).]

[Footnote 899: _Phil. Mag._, vol. xxviii. (4th ser.), p. 121.]

[Footnote 900: _Climate and Time_, 1875; _Discussions on Climate and
Cosm