hrichten_, Nos. 365-366. It should be
explained that what is called the "annual parallax" of a star is only
half its apparent displacement. In other words, it is the angle
subtended at the distance of that particular star by the _radius_ of the
earth's orbit.]

[Footnote 72: _Astr. Nach._, Nos. 401-402.]

[Footnote 73: Sir R. Ball's measurements at Dunsink gave to 61 Cygni a
parallax of 0.47"; Professor Pritchard obtained, by photographic
determinations, one of 0.43".]

[Footnote 74: _Additamentum in Mensuras Micrometricas_, p. 28.]

[Footnote 75: Elkin's corrected result (in 1897) for the parallax of
Vega is 0.082".]

[Footnote 76: _Mem. Roy. Astr. Soc._, vol. xi., p. 61.]

[Footnote 77: That numbered 21,185 in Lalande's _Hist. Cel._, found by
Argelander to have a proper motion of 4.734", and by Winnecke a parallax
of O.511". _Month. Not._, vol. xviii., p. 289.]

[Footnote 78: _Fund. Astr._, p. 309.]

[Footnote 79: _Mem. Pres. a l'Ac. de St. Petersb._, t. iii.]

[Footnote 80: _Phil. Trans._, vol. cxxxvii., p. 79.]

[Footnote 81: _Mem. Roy. Astr. Soc._, vols. xxviii. and xxxii.]

[Footnote 82: _Ibid._, vol. xlvii., p. 327.]

[Footnote 83: _Memoires de St. Petersbourg_, t. xxxv., No. 3, 1887;
revised in _Astr. Nach._, Nos. 3,729-30, 1901.]

[Footnote 84: _Astronomical Journal_, Nos. 213, 501.]

[Footnote 85: _Astr. Nach._, Nos. 2,999, 3,000.]

[Footnote 86: _Veroeffentlichungen der Grossh. Sternwarte zu Karlsruhe_,
Bd. iv., 1892.]

[Footnote 87: _Proceedings Amsterdam Acad. of Sciences_, Jan. 27, 1900.]

[Footnote 88: _Astr. Jour._, No. 457.]

[Footnote 89: _Ibid._, Nos. 276, 497.]

[Footnote 90: _Phil. Trans._, vol. xcvi., p. 230.]

[Footnote 91: _Mem. Pres. a l'Ac. de St. Petersbourg_, t. iii., p. 603
(read Feb. 5, 1837).]

[Footnote 92: _Die Centralsonne, Astr. Nach._, Nos. 566-567, 1846.]

[Footnote 93: Sir J. Herschel, note to _Treatise on Astronomy_, and
_Phil. Trans._, vol. cxxiii., part ii., p. 502.]

[Footnote 94: The position is (as Sir J. Herschel pointed out, _Outlines
of Astronomy_, p. 631, 10th ed.) placed beyond the range of reasonable
probability by its remoteness (fully 26 deg.) from the galactic plane.]

[Footnote 95: Maedler in _Westermann's Jahrbuch_, 1867, p. 615.]

[Footnote 96: Letter from Bessel to Sir J. Herschel, _Month. Not._, vol.
vi., p. 139.]

[Footnote 97: Wolf, _Gesch. d. Astr._, p. 743, _note_.]

[Footnote 98: _Astr. Nach._, Nos. 745-748.]

[Footnote 99: