._, 5(; DR. C. CHREE: SOME PHENOMENA OF SUNSPOTS 



preceding the representative disturbed day exceeds the fall in the two immediately 

 following days has been already noticed. This peculiarity is a prominent feature in 

 all the associated pulses in fig. 2, except the third previous, where the exact day of 

 incidence of the maximum is not clearly indicated. In the case of the selected quiet 

 days, on the other hand, the fall in the " character" figure in the two immediately 

 preceding days is less rapid than the rise in the two immediately succeeding days, 

 and the same peculiarity is reproduced in the first previous and the first and second 

 subsequent pulses. The second previous pulse shows the opposite phenomenon, but 

 this may arise from the same disturbing cause which has brought the maximum to 

 day 55 instead of day 54. In the third previous and third subsequent pulses the 

 shape of the curve is irregular. 



Speaking generally, in the case both of the disturbed and the quiet days, while 

 corresponding pulses respectively to right and left of the central line 00 are very 

 similar, the curves are not images of one another with respect to 00. The character 

 of the primary (i.e., central) pulse seems to be impressed on the associated pulses 

 which precede it, as well as on those which follow it. 



The curves for days 30 to 25 and for days +25 to +30 will have a much closer 

 fit if we cut the paper along the line 00, and bring the lines answering to days 27 

 and +27 over one another by sliding the one half sheet over the other, than if we 

 effect this superposition by folding the paper about the line 00. 



If the curves had been images of one another, by adding " character " figures for 

 days n+m and n m where n denotes the representative disturbed or quiet day 

 we might have got as smooth results for day m as if we had been able to use 12 years' 

 data while confirming ourselves to days following the selected days. The want of 

 symmetry makes the conditions somewhat less favourable for evaluating the length 

 of the period, supposing that not to be an exact number of days. The maxima at 

 days 54, 27 and +27 in the associated disturbed pulses are sufficiently prominent 

 to fairly justify the view that the true maxima lie within half a day of the apparent 

 maxima. This gives for the time of three periods 81 1 days, or for one period 

 27 0'3. 



The ordinates answering to days +54 and +55 differ but little, while those for 

 days +81 and +82 are practically equal. Thus the values deduced for the period 

 from these summits and that at day -54 are respectively 108'5/4, and 135'5/5 days, 

 or both approximately 271 days. 



On the curves associated with the selected quiet days, the maxima at days -81, 

 27, and +54 are the clearest. From-81 and +54 we get 27'0, and from -55 

 and + 54 we get 27*25 days. 



The associated disturbed curve for days -30 to -25 and the associated quiet curve 

 for days +25 to +30 both suggest slightly under 27 days for the period. 



11. If instead of treating the "character" figures from the disturbed and the 

 quiet associated days separately, we combine them, we obtain results of much greater 



