( 286 ) 



cvcloiies, pohir lights, iiiauiictic dctlectioiis are more frequent. l>ut 

 because at those times tlie mean temperature over the entire Earth 

 is some^vhat h)\ver than in the minima periods \) Ave come to the 

 conclusion that tlie total energy which reaches the Earth in maxima 

 of spot cycles must actually be less. This is our first objection to 

 anv exj)lanation l)ased on a periodical \ai-iatioii in the total output 

 of the Sun's energy. 



Now it migiit haj)pen that, altliong-h in years of spot maxima the 

 average output of solar enei-gy be lessened, the emission exhibits at 

 those times a greater varial)iHty than at minima. Various and numei'ous 

 obseivations have been nmh'rtaken with tlie object of ascertaining 

 whether the appearance of spots and taeniae, or their crossing the 

 central mericHan of the Sun, was generally accompanied by excessive 

 manifestations of terrestrial i)lienomena, and the results proved that 

 this was not invariably ihc case. An exliausti\e in(piiry into this 

 (|uesti()n has Ixm'ii i-ecenlly made by A. L. Cortik 'j. The investigations 

 of Fathkk SiiKiRKAVKs, extending over the years 1881 — 1896, had 

 alreadv clearly shown that periods of increased solar activity were 

 indeed marked by \ioIent magnetic storms, bul that many s|»ots were 

 not accompanied by magnetic dislui-bances and that such disturbances 

 often took place when the Sun was s|)ot-free. "These results", says 

 CoRTiK, "are advei-se to any theory n\ liicli would place the cause of 

 magnetic stoi-ms, and by the cause we mean the cflicient cause, any w here 

 oil or ill the \ iciuily of the Sun." He himself for three years (1899 — 

 1901) studied the appearances of the Sun's face in connexion with 

 the magnetic curves registered at Stonyhurst. He found that the 

 (iinniiil iiicdiis of s})Otted area and of the variations in declination 

 fairly agreed; but his table on p. '207 shows that this is not the case 

 when the average results for each single solar rotation are stutlied ; 

 and the immediate comparison of the daily solar observations \\\{\\ 

 the diurnal magnetic curves shows more clearly still, that spots and 

 disturbances do not necessarily always go together. For example, 

 during a great magnetic storm on Febr. 12^'^ 1899, the Sun was 

 almost entirely free from si)ots, and the very large spot observed 

 in May 1901, A\hicli i)ersisted during two solar rotations, was not 

 accompanied by any unusual magnetic disturbance. Cortie comes to 

 the conclusion that sun-si)ots and magnetic storms ])robably are 

 correlated as "two connected, though sometimes independent etfects 

 of one common cause." 



1) Gh. Nordmann, G. R. 136, p. 1047-1050, 1903. 



2) A. L. GoRTiE, S. J., Astrophysical Journal 16, p. 203—210, 1902. 



