The Stark effect has not been detected in the solar spectrum, presumably because the concentration of free electrons prevents the formation of large electrostatic fields. Several investigators, however, have contemplated in the Stark effect a possible factor influencing the stellar spectrum.[39][40] It does not seem unlikely that nuclear fields could operate as a sensible general electrostatic field at the photospheric level, thus producing a widening and winging of certain lines. The question has been numerically discussed by Hulburt,[41] and Russell and Stewart,[42] in an examination of Hulburt’s work, concluded that the Stark effect might possibly make some contribution (probably not a preponderant one) to the observed widths of lines in the solar spectrum. The question is not definitely settled, but it appears well to keep so important a possibility in mind. FOOTNOTES: [1] International Atomic Weights, 1917. [2] Aston, Isotopes, 1922; Phil. Mag., 47, 385, 1924; Nature, 113, 192, 856, 1924; Ibid., 114, 273, 716, 1924. Products of radioactive disintegration are omitted. [3] Clarke and Washington, Proc. N. Ac. Sci., 8, 108, 1922. [4] Bohr, Naturwiss., 11, 619, 1923. [5] Sommerfeld, Atombau und Spektrallinien, 3d. edition, 286, 1922. [6] A. Fowler, Proc. Roy. Soc., 105A, 299, 1924. [7] Sommerfeld, Atombau und Spektrallinien, 3d edition, 457, 1922. [8] Meggers, Kiess, and Walters, J. Op. Soc. Am., 9, 355, 1924. [9] A. Fowler, Report on Series in Line Spectra, 1922; Bakerian Lecture, 1924. [10] Paschen, An. d. Phys., 71, 151, 1923. [11] Sommerfeld, Atombau und Spektrallinien, 3d. edition, 255, 1922; A. Fowler, Proc. Roy. Soc., 90A, 426, 1913; Paschen, An. d. Phys., 50, 901, 1919. [12] H. H. Plaskett, Pub. Dom. Ap. Obs., 1, 348, 1922. [13] P. 156. [14] Millikan and Bowen, Phys. Rev., 23, 1, 1924; Nature, 114, 380, 1924. [15] Hartree, Proc. Camb. Phil. Soc., 22, 464, 1924; Thomas, Phys. Rev., 25, 322, 1925. [16] Verh. d. Deutsch. Phys. Ges., 21, 728, 1919. [17] Phil. Mag., 46, 872, 1923. [18] Proc. Roy. Soc., 103A, 121, 1923. [19] Proc. N. Ac. Sci., 10, 322, 1924. [20] Proc. Phys. Soc. Lond., 36, 94, 1924. [21] An. d. Phys., 43, 96, 1914. [22] Phys. Zeit., 18, 121, 1917. [23] Phys. Zeit., 21, 322, 1922. [24] Proc. Copenhagen Ac., 1919. [25] Physica, 4, 337, 1924. [26] Physica, 4, 340, 1924. [27] Zeit. f. Tech. Phys., 5, 2, 1925. [28] Atombau und Spektrallinien, 3d edition, 588, 1922. [29] Physica, 3, 188, 1923; Zeit. f. Phys., 13, 206, 1923; ibid., 22, 270, 1924; Dissertation, Utrecht, 1924; Physica, 5, 27, 1925. [30] King, Mt. W. Contr. 53, 1911; ibid., 60, 1912. [31] St. John and Babcock, Ap. J., 60, 32, 1924. [32] Zeemann, Researches in Magneto-Optics, 1911. [33] Hale, Mt. W. Contr. 30, 1908. [34] Landé, Zeit. f. Phys., 15, 189, 1923. [35] Stark, Elektrische Spektralanalyse Chemischer Atome, 1914. [36] Merton, Proc. Roy. Soc., 92A, 322, 1915; ibid., 95A, 33, 1919. [37] Anderson, Mt. W. Contr. 134, 1917.