288 



Dr. W. J. S. Lockyer. 



The Sunspot and Magnetic Epochs employed. 



As this paper deals mainly with the times of minima and maxima 

 of both the sunspot and magnetic curves, it was necessary to utilise 

 the results obtained from curves which had been " smoothed," as the 

 original curves are of a subsidiary oscillatory character, especially at 

 maximum. 



The sunspot curves just referred to are reproduced in fig. 1. They 

 are so arranged in order of date that each individual curve can be 

 examined separately. The times of succeeding minima are arranged 

 vertically under each other, so that any variation as regards accelera- 

 tion or retardation of the following maxima, and any inequality in the 

 length of the period minimum to minimum can be seen at a glance. 



Up to the sunspot maximum of 1870-6 Dr. Wolf has published* 

 the dates of these epochs, and these are utilised here. The more 

 recent epochs have been brought together by Mr. Ellis, f and these 

 complete the data available up to the last epoch, namely, the maximum 

 of 1894-0. 



Each of these epochs is indicated in fig. 1 by a short arrow with 

 the corresponding dates. The magnetic epochs here used are those 

 published by Mr. Ellis in the paper just mentioned, and obtained from 

 curves smoothed similarly to those of the sunspot curves. Unfortu- 

 nately the observations he discussed only commenced in the beginning 

 of 1841, so that comparisons cannot be made previously to this date. 



The smoothed curves obtained by Mr. Ellis are not here reproduced, 

 but they will be found in his valuable paper J published in 1880. 



The Sunspot Curves. Minimum to Maximum. 



In the following table are brought together the dates of the epochs 

 of maxima and minima : — ■ 



Sunspot epochs (Wolf). 



Maximum 

 minus 



minimum 

 years. 



Minimum. 



Maximum. 



(1) 1833 -9 



(2) 1843-5 



(3) 1856 



(4) 1867-2 



(5) 1879-0 



(6) 1890 -2 



1837 -2 

 1848-1 

 1860-1 

 1870-6 

 1884 -0 

 1894 -0 



3- 3 



4- 6 



4- 1 

 3-4 



5- 

 3-8 



Mean 4 -03 



* ' Mem. E. Astron. Soc.,' vol. 43, p„ 202. 



f ' Roy. Soc. Proc ,' vol. 63, p. 67. 



X ' Phil. Trans.,' 1880, Part II, Plate 22. 



