1. In a previous paper, described here for brevity as S.M., which referred to sunspots and terrestrial magnetism, I had occasion to enquire into the existence of any relation between the magnetic character of individual days and that of days separated from them by a given interval of time. References to previous work bearing on the subject will be found in S. M., p. 97. The material of which I made principal use consisted of magnetic “character” figures—on the international scale 0 (quiet), 1 (moderately disturbed), and 2 (highly disturbed)—assigned by myself to all the days of the eleven years 1890 to 1900, from consideration of the Kew magnetic curves.