BETWEEN SUN-SPOT FREQUENCY AND TERRESTKIAL MAGNETISM. 



153 



the method of least squares. The formulae he thus obtains, and one which he quotes 

 as obtained by WOLFER, are as follows : 



EAJNA . . . 

 WOLFER 



1836 to 1894, E = 5-31 + 0'047 S 

 1871 1894, E = 5-39 + 0-047 S 

 K = 5-67 + 0-040 S 



. (II.), 

 . (III). 



WOLFEB'S value 0'040 for b is based on data from Christiania, Prague, Greenwich 

 and Vienna, as well as from Milan. HAJNA compares the values calculated from each 

 of the three formulae with the ranges observed at Milan from 1836 to 1901. 

 Formula (I.) agrees rather better than (II.) with observation; formula (III.) seems 

 distinctly inferior. The difference between the observed values arid those calculated 

 from (I.) varies from l''87 in 1838 to + 1''87 in 1866, the extreme values observed 

 in E, being 4'"21 and 12'"03. Since 1871 the agreement seems decidedly improved. 

 Over the 24 years for which it was originally calculated (II.) gives a " probable error " 

 of only 0'-21, the difference between observed and calculated values varying from 

 0''49 to + 0'-53. 



EAJNA himself notices that there are several long runs of the same sign in the 

 differences between observed and calculated values. Thus from 1H37 to 1850 the 

 observed value is in excess of the calculated (from either (I.) or (II.)) 12 out of 14 

 times; on the other hand, in the 14 years 1854 to 1867, the calculated value is 13 

 times in excess. In the 11 years 1890 to 1900 (to which the Kew data treated in 

 (A) referred) EAJNA' s calculated value from either (I.) or (II.) has been in excess 

 8 times, including every year since 1893. 



The two first specified predominances of one sign are certainly in excess of what 

 one would expect from pure chance. To throw some further light on the question, I 

 have calculated values for a and b for the above-mentioned series of years. Instead 

 of least squares, I grouped the years, following the method explained in (A), 52. 

 The grouping of years and the corresponding mean values of E and S were as 

 follows : 



Period 1837 to 1850 



Years of sun-spot maximum, 1837, 1838, 1839, 1847, 1848, 1849 . . 



minimum, 1841 to 1845 



Period 1854 to 1867 



Years of sun-spot maximum, 1858 to 1862 



minimum, 1854, 1855, 1856, 1865, 1866, 1867 . . 



Period 1890 to 1900 



Years of sun-spot maximum, 1892 to 1895 



minimum, 1890, 1899, 1900 



Mean K. 



9-270 



10-950 



7-552 



6-586 

 8-176 

 5-245 



7-163 

 8-753 

 5-587 



Mean S. 



68-9 



107-7 



L'5-4 



41-4 

 76-1 

 14-3 



41-7 



75-0 



9-5 



VOL. CCII1. A. 



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