The 4.79 Period of Sun-spot Activity

Abstract

IN NATURE of August 13 (p. 351) the photograph is published of two groups of sun-spots taken on August 6, and attention is directed to the remarkable fact that such an outbreak should occur two years after the sun-spot maximum. This renewed sun-spot activity is connected with the 4.79 period, which I have shown to have been quite persistent—even more so than the eleven-year period—since sun-spots were first systematically observed. In a paper published in the Philosophical Transactions for 1906 I gave the times of maxima of this period as being 1903.72+4.79 n. This would bring the maximum to 1908.51, or to about July 1 of the present year. A retardation of one month in a period of more than four years' duration is, of course, insignificant.