TEREESTRIAL MAGNETISM AT KEW OBSERVATORY. 
83 
Sunspot Areas. 
§ 9. In the subsequent comparisons of sunspot areas and magnetic phenomena use 
was made not merely of the whole 11 years 1890 to 1900, but also of the following 
groups of these years :— 
1890, 1899, and 1900 representing sunspot minimum; 
1891, 1895, and 1896 representing the most rapid portion of the rise of sunspot 
areas to the maximum and their subsequent decline, and also representing 
an exceptionally high average state of magnetic disturbance ; 
All the years (8) except those in the last-mentioned group ; 
1892, 1893, and 1894 representing sunspot maximum. 
In the case of the 11 years, the three seasons winter, equinox, and summer, as 
defined in § 3, were also considered separately. 
In the case of the sunspot maximum years there were two investigations, one based 
as in the other cases on the 5 days a month of largest spot area, the other on the 5 
days a month of least spot area. The sunspot area data derived from these investi¬ 
gations appear in Table IV. Column n gives the characteristics of the representative 
of the selected 5 days a month. The columns n —15 to n—1 give the characteristics 
of the 15 days immediately preceding the representative day, columns n-tl to n + lb 
the characteristics of the 15 days immediately following the representative day. The 
figures in these 31 columns represent percentages of the mean spot area, dej’ived from 
the whole 31 columns. 
The method aims at securing a pulse of high (or low) spot area centering at day n, 
and our immediate object is to ascertain the form of that pulse. 
§ 10. The 11-year data in the first line of Table IV. are shown graphically in the 
full line curve of fig. 1. They represent an exceedingly smooth and nearly symmetrical 
M 2 
