ANH oi TERRESTRIAL MACNRTIS.M. 



disturl>cd days of the five years 1906 to 1910. The investigation was 

 restricted to the seven days n 3 to n + 3. The results for the several years appear 

 in Tahle XL, the figures being expressed as percentages of the normal value of the 

 quantity concerned for the year in question. 



TABLE XI. Relation of Sunspot Areas and Frequencies and of Faculee to Magnetic 

 DisturlKince (?/, Ix-ing Representative Day of Large Disturlmnce). 



Of the two sets of mean values given in the last two lines of Table XL, the first 

 are arithmetic means of the percentages for the individual years ; the second were 

 obtained by summing the area or frequency figures for the 300 days in each column, 

 and expressing the mean as a percentage of the corresponding mean derived from all 

 days of five years. 



Table XL shows that, at least for the years considered, it does not much matter 

 whether projected or corrected spot areas are taken for comparison with magnetic 

 disturbances. If anything, the projected percentages are a trifle the larger. We 



VOL. CCXIII. A. 



2 N 



