[Footnote 365: _Die Sonne und ihre Flecken_, p. 30. Arago was the first who attempted to decide the question by keeping, through a series of years, a parallel register of sun-spots and weather; but the data regarding the solar condition amassed at the Paris Observatory from 1822 to 1830 were not sufficiently precise to support any inference.] [Footnote 366: _Phil. Trans._, vol. xxix., p. 421.] [Footnote 367: _Ibid._, vols. cxliii., p. 558, cxlvi., p. 505.] [Footnote 368: _Observations on Light and Colours_, p. 35.] [Footnote 369: _Phil. Trans._, vol. lxxv., p. 190.] [Footnote 370: _Denkschriften_ (Munich. Ac. of Sc.), 1814, 1815, Bd. v., p. 197.] [Footnote 371: _Edinburgh Journal of Science_, vol. v., p. 77. See also _Phil. Mag._, Feb., 1834, vol. iv., p. 112.] [Footnote 372: _Ed. Phil. Trans.,_ vol. xxi., p. 411.] [Footnote 373: _On the Absorption of Light by Coloured Media, Ed. Phil. Trans._, vol. ix., p. 445 (1823).] [Footnote 374: _Phil. Mag._, vol. xxvii, (ser. iii.), p. 81.] [Footnote 375: _Report Brit. Ass._, 1835, p. 11 (pt. ii.). _Electrodes_ are the terminals from one to the other of which the electric spark passes, volatilising and rendering incandescent in its transit some particles of their substance, the characteristic light of which accordingly flashes out in the spectrum.] [Footnote 376: _Phil. Mag._, vol. xx., p. 93.] [Footnote 377: _Annalen der Physik_, Bd. cxiii., p. 357.] [Footnote 378: _Phil. Trans._, vol. xcii., p. 378.] [Footnote 379: _Denkschriften_, Bd. v., p. 202.] [Footnote 380: _Ibid._, p. 220; _Edin. Jour. of Science_, vol. viii., p. 9.] [Footnote 381: _Denkschriften_, Bd. v., p. 222.] [Footnote 382: _Arch. des Sciences_, 1849, p. 43.] [Footnote 383: _Phil. Trans._, vol. cl., p. 159, _note_.] [Footnote 384: _Ed. Phil. Trans._, vol. xii., p. 528.] [Footnote 385: _Phil. Trans._, vol. cxxvi., p. 453. "I conceive," he says, "that this result proves decisively that the sun's atmosphere has nothing to do with the production of this singular phenomenon" (p. 455). And Brewster's well-founded opinion that it had much to do with it was thereby, in fact, overthrown.] [Footnote 386: _Monatsberichte_, Berlin, 1859, p. 664.] [Footnote 387: _Abhandlungen_, Berlin, 1861, pp. 80, 81.] [Footnote 388: _Ibid._, 1861, p. 77; _Annalen der Physik_, Bd. cxix., p. 275. A similar conclusion, reached by Balfour Stewart in 1858, for heat-rays (_Ed. Phil. Trans._, vol. xxii., p. 13), was, in 1860, without previous knowledge of Kirchhoff's work, extended to light (_Phil. Mag._, vol. xx., p. 534); but his experiments wanted the precision of those executed at Heidelburg.] [Footnote 389: _Miscellaneous Works_, vol. i., p. 189.] [Footnote 390: _Ed. Phil. Trans._, vol. ix., p. 458.] [Footnote 391: _Ibid._, vol. xii., p. 519.] [Footnote 392: _Quart. Jour. Chem. Soc._, vol. x. p. 79.] [Footnote 393: A facsimile accompanied Sir H. Roscoe's translation of Kirchhoff's "Researches on the Solar Spectrum" (London, 1862-63).]