in very close agreement with observations.
[30] J. J. Thomson, Phil. Mag. xxiv. p. 218 (1912).
[31] J. Franck u. G. Hertz, Verh. d. Deutsch. Phys. Ges. xv. p. 34 (1913).
[32] C. and M. Cuthbertson, Proc. Roy. Soc. A. lxxxiv. p. 13 (1910). (In a previous paper (Phil. Mag. Jan. 1913) the author took the values for the refractive index in helium, given by M. and C. Cuthbertson, as corresponding to atmospheric pressure; these values, however, refer to double atmospheric pressure. Consequently the value there given for the number of electrons in a helium atom calculated from Drude’s theory has to be divided by 2.)
[33] See J. Franck, Verh. d. Deutsch. Phys. Ges. xii. p. 613 (1910).
[34] J. W. Nicholson, Month. Not. Roy. Astr. Soc. lxxiii. p. 382 (1913).
[35] Comp. J. J. Thomson, Phil. Mag. xxiii. p. 456 (1912).
[36] R. Whiddington, Proc. Roy. Soc. A. lxxxv. p. 323 (1911).
[37] Comp. E. Rutherford, Phil. Mag. xxiv. p. 453 (1912).
[38] See A. S. Russell and R. Rossi, Proc. Roy. Soc. A. lxxxvii. p. 478 (1912).