The minute vibrations of the magnetic needle, thus carefully watched—day after day, month after month, year after year—were found to exhibit a yet more minute oscillatory change. They waxed and waned within narrow limits of variation, but yet in a manner there was no mistaking. The period of this oscillatory change was not to be determined, however, by the observations of a few years. Between the time when the diurnal vibration was least until it had reached its greatest extent, and thence returned to its first value, no less than ten and a half years elapsed, and a much longer time passed before the periodic character of the change was satisfactorily determined. The reader will at once see what these observations tend to. The sun spots vary in frequency within a period of ten and a half years, and the magnetic diurnal vibrations vary within a period of the same duration. It might seem fanciful to associate the two periodic series of changes together, and doubtless when the idea first occurred to Lamont, it was not with any great expectation of finding it confirmed that he examined the evidence bearing on the point. Judging from known facts, we may see reasons for such an expectation in the correspondence of the needle’s diurnal vibration with the sun’s apparent motion, and the law which has been found to associate the annual variations of the magnet’s power with the sun’s distance. But undoubtedly when the idea occurred to Lamont it was an exceedingly bold one, and the ridicule with which the first announcement of the supposed law was received, even in scientific circles, suffices to show how unexpected that relation was which is now so thoroughly established. For a careful comparison between the two periods has demonstrated that they agree most perfectly, not merely in length, but maximum for maximum, and minimum for minimum. When the sun spots are most numerous, then the daily vibration of the magnet is most extensive, while, when the sun’s face is clear of spots, the needle vibrates over its smallest diurnal arc.