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).]

[Footnote 394: Estimated by Kirchhoff's at a _trillion to one_.
_Abhandl._, 1861, p. 79.]

[Footnote 395: _Phil. Mag._, vol. xxvii. (3rd series), p. 90.]

[Footnote 396: _L'Institut_, Feb. 7, 1849, p. 45; _Phil. Mag._, vol.
xix. (4th series), p. 193.]

[Footnote 397: _Ann. d. Phys._, vol. cxviii., p. 110.]

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