266 
DR. C. CHREE: DISCUSSION OF IvEW MAGNETIC DATA 
Taking the arithmetic mean of the monthly values of R in H for each year of the 
eleven, and applying the ft = a + b S formula, I found by least squares 
a = 21‘47y, 6 = 0'2224y, 100 6/a = 1'036. 
The division of the year into equal groups of 6 months only partly attains the 
object in view, viz., the elimination of any cause whose effect lasts for several months, 
because there is some tendency for the months of higher S in a year to occur together. 
In 1890, for instance, the 6 months of largest S came from the second half of the 
year, while in 1894 and 1900 the first half of the year contributed 5 out of the 6 months 
in the first group. Taking this into account, and the smallness of the value of b/a 
deduced in the case of R from Table XLIV., the natural inference would seem to be 
that the value of R from ordinary days in a particular month depends less on the 
value of S in that month than on the values of S in the other months of the year. 
This may mean nothing more than that the value of S on a particular day is a very 
rough measure of the solar activity to which enhanced diurnal inequalities are due, 
while the mean value of S from all days of the year affords a very exact measure. 
The fact that the value of b/ct derived from Table XLIV. in the case of R' is so 
much larger than that derived in the case of R, suggests that the solar influence is 
more direct or immediate in the case of irregular than in the case of regular magnetic 
changes. 
Table XLV. shows the result of grouping the 132 months according to the monthly 
mean value of S. Notwithstanding the considerable number of months included in 
the groups, the results of the first grouping in which the step in S is only 10 are 
somewhat irregular. R and IT show a decided tendency throughout to increase with 
Table XLV. — Percentage Ranges from Months Grouped according to Sunspot 
Frequency. 
Range of 
values 
of S. 
Montlis 
in 
group. 
Mean values; 
S. 
R 
per cent. 
R' 
per cent. 
0 to 10 
23 
6-2 
77-8 
71-5 
10 „ 20 
20 
13-8 
75-1 
77-7 
20 „ 30 
14 
25-1 
93-0 
94-6 
30 „ 40 
12 
33-7 
89-5 
98-7 
40 „ 50 
12 
45-4 
103-0 
106-7 
50 „ 60 
8 
55-0 
111-5 
112-9 
60 „ 70 
14 
65-4 
120-2 
112-6 
70 „ 80 
16 
75-2 
125-4 
129-6 
80 „ 90 
7 
85-6 
128-7 
124-1 
>90 
6 
105-1 
137-0 
132-0 
Range of 
values 
of S. 
Months 
in 
group. 
Mean values. 
S. 
R 
per cent. 
R' 
per cent. 
0 to 20 
43 
9-6 
76-6 
74-4 
20 „ 40 
26 
29-1 
91-4 
96-5 
40 „ 60 
20 
49-3 
106-4 
109-2 
60 „ 80 
30 
70-6 
123-0 
121-7 
>80 
13 
94-6 
132-5 
127-8 
