[485] See J. Rand Capron, Phil. Mag., vol. xv., p. 318.
[486] Mittheilungen über die Sonnenflecken, No. ix., Vierteljahrsschrift der Naturforschenden Gesellschaft in Zürich, Jahrgang 4.
[487] Mitth., No. lii., p. 58 (1881).
[488] Ibid., No. xii., p. 192. Baxendell, of Manchester, reached independently a similar conclusion. See Month. Not., vol. xxi., p. 141.
[489] Wolf, Mitth., No. xv., p. 107, etc. Olmsted, following Hansteen, had already, in 1856, sought to establish an auroral period of sixty-five years. Smithsonian Contributions, vol. viii., p. 37.
[490] Hahn, Ueber die Reziehungen der Sonnenfleckenperiode zu meteorologischen Erscheinungen, p. 99 (1877).
[491] Report Brit. Ass., 1881, p. 518; 1883, p. 418.
[492] The Rev. A. Cortie (Month. Not., vol. lx., p. 538) detects the influence of a short subsidiary cycle, Dr. W. J. S. Lockyer that of a thirty-five year period (Nature, June 20, 1901). Professor Newcomb (Astroph. Jour., vol. xiii., p. 11) considers that solar activity oscillates uniformly in 11.13 years, with superposed periodic variations.
[493] Opere, t. iii., p. 412.
[494] Mitth., Nos. vii. and xviii.