[Footnote 655: Many of these were referred by Lockyer himself, who first
sifted the matter, to traces of the metals concerned.]

[Footnote 656: _Chemistry of the Sun_, p. 312; _Proc. Roy. Society_,
vol. lvii., p. 199.]

[Footnote 657: _Lockyer's Chemistry of the Sun_, p. 324.]

[Footnote 658: _Month. Not._, vol. li., p. 76.]

[Footnote 659: _Ibid._, vol. lviii., p. 370.]

[Footnote 660: _Astr. and Astrophysics_, vol. xi., p. 615.]

[Footnote 661: Thollon's estimate (_Comptes Rendus_, t. xcvii., p. 902)
of 300,000 _kilometres_, seems considerably too low. Limiting the
"average prominence region" to a shell 54,000 miles deep (2' of arc as
seen from the earth), the visual line will, at mid-height (27,000 miles
from the sun's surface), travel through (in round numbers) 320,000 miles
of that region.]

[Footnote 662: Liveing and Dewar, _Phil. Mag._, vol. xvi. (5th ser.), p.
407.]

[Footnote 663: _Chemistry of the Sun_, p. 260.]

[Footnote 664: _Nature_, October 14, 1886.]

[Footnote 665: The normal spectrum is that depending exclusively upon
wave-length--the fundamental constant given by nature as regards light.
It is obtained by the interference of rays, in the manner first
exemplified by Fraunhofer, and affords the only unvarying standard for
measurement. In the refraction spectrum (upon which Kirchhoff's map was
founded), the relative positions of the lines vary with the material of
the prisms.]

[Footnote 666: Scheiner, _Die Spectralanalyse der Gestirne_, p. 168.]

[Footnote 667: _Phil. Mag._, vol. xxvii., p. 479.]

[Footnote 668: _Astr. and Astrophysics_, vol. xii., p. 321;
Frost-Scheiner, _Astr. Spectr._, p. 363.]

[Footnote 669: Published in _Astroph. Jour._, vols. i. to vi.]

[Footnote 670: _Astr. and Astrophysics_, vol. xi., p. 793.]

[Footnote 671: _Astroph. Jour._, vol. vi., p. 95.]

[Footnote 672: _Annales de l'Observatoire de Nice_, t. iii., 1890.]

[Footnote 673: _Trans. Royal Society of Edinburgh_, vol. xxxvi., p. 99.]

[Footnote 674: Rev. A. L. Cortie, _Astr. and Astrophysics_, vol. xi., p.
401. Specimens of his photographs were given by Ranyard in _Knowledge_,
vol. xiii., p. 212.]

[Footnote 675: _Ann. d. Phys._, Bd. cxvii., p. 296.]

[Footnote 676: _Comptes Rendus_, t. lxiii., p. 647.]

[Footnote 677: _Ibid._, t. lxxxvi., p. 317. Some half dozen of these
identifications have proved fallacious.]

[Footnote 678: _Chemistry of the Sun_, p. 143.]

[Footnote 679: _Amer. Jour. of Sc