THE sun's spots. Si 



ihat occur in accessible portions of our Earth. Without as« 

 suming magnetic poles in the Sun's body, or any special mag- 

 netic forces in the solar rays, the central body may, as a pow- 

 erful source of heat, excite magnetic activity on our planet. 



The attempts that have been made to prove, by means of 

 meteorological observations prosecuted Jbr many years at in- 

 dividual spots, that one side of the Sun (for instance, the side 

 which was turned toward the Earth on the 1st of January, 

 1846) possesses a more intsnse heating power than the oppo- 

 site one,^ have not led to more reliable results than the older 

 Greenwich observations of Maskeleyne, which were supposed 

 to prove that the Sun had decreased in diameter. 



The observations made by Counselor Schwabe, of Dessau, 

 for reducing the periodicity of the Sun's spots to definite nu- 

 merical relations, appear to have a surer foundation. No as- 

 tronomer of the present day, however admirable may have 

 been his instruments, could have devoted his attention more 

 continuously to this subject than Schwabe, who, during the 

 long period of twenty-four years, frequently examined the 

 Sun's disk upward of 300 days in the year. As his observa- 

 tions of the Sun's spots from 1844 to 1850 have not yet been 

 published, I have presumed so far on our friendship as to re- 

 quest that he would communicate them to me, and at the 

 same time answer a number of questions which I proposed 

 to him. I wdll close this section of the Physical Constitu- 

 tion of our Central Body with the observations with which 

 this observer has allowed me to enrich the astronomical por- 

 tion of my work. 



" The numbers contained in the following table leave no 

 doubt that, at least from the year 1826 to 1850, the occur- 

 rence of spots has been so far characterized by periods of ten 

 years, that its maxima have fallen in the years 1828, 1837, 

 and 1848, and its minima in the years 1833 and 1843. I 

 have had no opportunity," says Schwabe, " of acquainting 

 myself with the older observations in a continued series, but 

 I willingly .concur in the opinion that this period may itself 

 be further characterized by variability."! 



* Compare Nervander of Helsingfors, in the Bulletin de la CtasM 

 Physico-MathSm. de VAcad. de St.Pitersbourg, torn, iii., 1845, p. 3U-32 ; 

 End Buys-Ballot, of Utrecht, iu Poggend., Annalen der Physik, vol 

 Ixviii., 1846, p. 205-213. 



t I have distinguished by inverted commas the quotations from 

 Schwabe's manuscript communications from p. 85-87. Only the ob 

 servations of the years 1826 to 1843 have already been published in 

 Schumacher's Adron. Nackr., No. 495 (bd. xxi., 1844), p. 235 



