erature
with radiation. Stefan's rule of a fourth-power relation, if not
actually a law of nature, is a colourable imitation of one; and its
employment has afforded a practical certainty that the sun's
temperature, so far as it is definable, neither exceeds 12,000 deg. C.,
nor falls short of 6,500 deg. C.

FOOTNOTES:

[Footnote 698: _Principia_, p. 498 (1st ed.).]

[Footnote 699: _Comptes Rendus_, t. vii., p. 24.]

[Footnote 700: _Results of Astr. Observations_, p. 446.]

[Footnote 701: "Est enim calor solis ut radiorum densitas, hoc est,
reciproce ut quadratum distantiae locorum a sole."--_Principia_, p. 508
(3d ed., 1726).]

[Footnote 702: _Jour. de Physique_, t. lxxv., p. 215.]

[Footnote 703: _Ann. de Chimie_, t. vii., 1817, p. 365.]

[Footnote 704: _Phil. Mag._, vol. xxiii. (4th ser.), p. 505.]

[Footnote 705: _Nuovo Cimento_, t. xvi., p. 294.]

[Footnote 706: _Comptes Rendus_, t. lxv., p. 526.]

[Footnote 707: The direct result of 5-1/3 million degrees was doubled in
allowance for absorption in the sun's own atmosphere. _Comptes Rendus_,
t. lxxiv., p. 26.]

[Footnote 708: _Ibid._, p. 31.]

[Footnote 709: _Nature_, vols. iv., p. 204; v., p. 505.]

[Footnote 710: _Ibid._, vol. xxx., p. 467.]

[Footnote 711: _Ann. de Chim._, t. x. (5th ser.), p. 361.]

[Footnote 712: _Comptes Rendus_, t. xcvi., p. 254.]

[Footnote 713: _Phil. Mag._, vol. viii., p. 324, 1879.]

[Footnote 714: _Ibid._, p. 325.]

[Footnote 715: _Sitzungsberichte_, Wien, Bd. lxxix., ii., p. 391.]

[Footnote 716: _Wiedemann's Annalen_, Bd. xxii., p. 291; _Scheiner,
Strahlung und Temperatur der Sonne_, p. 27.]

[Footnote 717: _Comptes Rendus_, March 28, 1892; _Astr. and
Astrophysics_, vol. xi., p. 517.]

[Footnote 718: _Phil. Trans._, vol. clxxxv., p. 361.]

[Footnote 719: _Proc. Roy. Society_, December 12, 1901.]

[Footnote 720: Scheiner, _Temp. der Sonne_, p. 36.]

[Footnote 721: _Astroph. Jour._, vol. ii., p. 318.]

[Footnote 722: _Astr. Nach._, Nos. 1,815-16.]

[Footnote 723: _L'Astronomie_, September, 1884, p. 334.]

[Footnote 724: _Amer. Jour. of Science_, vol. i. (3rd ser.), p. 653.]

[Footnote 725: Young, _The Sun_, p. 310.]

[Footnote 726: _Op._, t. vi., p. 198.]

[Footnote 727: _Rosa Ursina_, lib. iv., p. 618.]

[Footnote 728: _Mec. Cel._, liv. x., p. 323.]

[Footnote 729: _Le Soleil_ (1st ed.), p. 136.]

[Footnote 730: _Monatsber._, Berlin, 1877, p. 104.]

[Footnote 731: _Astr. Nach._, Nos. 3,105-6;