Long-period variations in solar phenomena are shown by the relative numbers at epochs of maxima and the intervals between successive maxima or minima. Intensity values are available only from 1750, or the date of the beginning of the Wolfer relative numbers. The interval values are derived from the Wolfer epochs from 1611 and from the epochs of maxima beginning 301 A.D., first derived by Fritz and revised by the writer. There is a high negative correlation between the intensity at a maximum and the interval from the preceding minimum.
The epochs of maximum and minimum auroral frequency, available since 1611, and of magnetic declination range since 1775, afford an independent check on the reliability of the Wolfer epochs. A change in two of the epochs of maxima is suggested.
The reliability of the Fritz ancient epochs is confirmed by a graphical device, showing the continuity of the 11-year epochs since 301.
The existence of long-period variations in the length of the 11-year period is shown by a graphical periodicity tabulation of the 11-year intervals since 301. A 37-year period is shown by the existence of maxima every third or fourth interval, and an 83-year period is shown by a similar tabulation of the smoothed intervals. These periods are also obtained by the rigid method of self-correlation of the 11-year intervals, and numerous series of terrestrial data yield by self-correlation the same periods. The meteorological effects following certain solar changes are briefly summarized.