36 LIGHT SCIENCE FOR LEISURE HOURS. 



years, it was found that there was an alternate and 

 systematic increase and diminution in the intensity of 

 magnetic action, and that the period of the variation 

 was about eleven years. But at the same time, a dili- 

 gent observer had been recording the appearance of the 

 sun's face from day to day and from year to year. He 

 had found that the solar spots are in some years more 

 freely displayed than in others. And he had deter- 

 mined the period in which the spots are successively 

 presented with maximum frequency to be about eleven 

 years. On a comparison of the two sets of observa- 

 tions, it was found (and has now been placed beyond a 

 doubt by many years of continued observation) that 

 magnetic perturbations are most energetic when the 

 sun is most spotted, and vice versa. 



For so remarkable a phenomenon as this none but 

 a cosmical cause can suffice. We can neither say 

 that the spots cause the magnetic storms nor that the 

 magnetic storms cause the spots. We must seek for a 

 cause producing at once both sets of phenomena. 

 There is as yet no certainty in this matter, but it 

 seems as if philosophers would soon be able to trace 

 in the disturbing action of the planets upon the solar 

 atmosphere the cause as well of the marked period of 

 eleven years as of other less distinctly marked periods 

 which a diligent observation of solar phenomena is 

 beginning to educe. 



(From the Cornhitt Magazine, June 1868.) 



