[Footnote 279: Hind, _The Comets_, p. 47.] [Footnote 280: Arago, _Annuaire_, 1836, p. 228.] [Footnote 281: _Astr. Nach._, No. 300.] [Footnote 282: It deserves to be recorded that Robert Hooke drew a very similar inference from his observations of the comets of 1680 and 1682. _Month. Not._, vol. xiv., pp. 77-83.] [Footnote 283: _Briefwechsel zwischen Olbers und Bessel_, Bd. ii., p. 390.] [Footnote 284: Herschel, _Results_, p. 405.] [Footnote 285: _Mem. R. A. S._, vol. x., p. 92,] [Footnote 286: _Results_, p. 401.] [Footnote 287: Pontécoulant, _Comptes Rendus_, t. lviii., p. 825.] [Footnote 288: _Annuaire_, 1836, p. 233.] [Footnote 289: _Cosmos_, vol. i., p. 90, _note_ (Otté's trans.).] [Footnote 290: Herschel, _Outlines of Astronomy_, p. 399, 9th ed.] [Footnote 291: _Outlines_, p. 398.] [Footnote 292: Boguslawski calculated that it extended on the 21st of March to 581 millions.--_Report. Brit. Ass._, 1845, p. 89.] [Footnote 293: _Comptes Rendus_, t. xvi., p. 919.] [Footnote 294: _Observatory_, vol. xxiv., p. 167; Astr. Nach., No. 3,320.] [Footnote 295: Piazzi noticed a considerable increase of lustre in a very faint star of the twelfth magnitude viewed through a comet. Mädler, _Reden_, etc., p. 248, _note_.] [Footnote 296: _Astr. Jahrbuch_, 1828, p. 151.] [Footnote 297: Mädler, _Gesch. d. Astr._, Bd. ii., p. 412.] [Footnote 298: _Recueil de l'Ac. Imp. de St. Pétersbourg_, 1835, p. 143.] [Footnote 299: Guillemin's _World of Comets_, trans, by J. Glaisher, p. 294, _note_.] [Footnote 300: _Month. Not._, vol. viii., p. 9.] [Footnote 301: A real, though only partial stoppage of light seems indicated by Herschel's observations on the comet of 1807. Stars seen through the tail, October 18, lost much of their lustre. One near the head was only faintly visible by glimpses. _Phil. Trans._, vol. xcvii., p. 153.] [Footnote 302: Arago, _Annuaire_, 1832, p. 205.] [Footnote 303: _Ibid._, 1891, p. 290.] [Footnote 304: Viz., Encke's, Biela's, Faye's, and Brorsen's.] CHAPTER VI _INSTRUMENTAL ADVANCES_ It is impossible to follow with intelligent interest the course of astronomical discovery without feeling some curiosity as to the means by which such surpassing results have been secured. Indeed, the bare acquaintance with _what_ has been achieved, without any corresponding knowledge of _how_ it has been achieved, supplies food for barren wonder rather than for fruitful and profitable thought. Ideas advance most readily along the solid ground of practical reality, and often find true sublimity while laying aside empty marvels. Progress is the result, not so much of sudden flights of genius, as of sustained, patient, often commonplace endeavour; and the true lesson of scientific history lies in the close connection which it discloses between the most brilliant developments of knowledge and the faithful accomplishment of his daily task by each individual thinker and worker.