DR. C. CHREE: DISCUSSION OF KEW MAGNETIC DATA 
Table LIII.—Vertical Force Ranges (Unit ly). Number of Occurrences 
in Eleven Years. 
Month. 
From 0 
To 12-5 
12-5 
25 
25 
37-5 
37-5 
50 
50 
62-5 
62-5 
75 
75 
100 
100 
125 
125 
150 
150 
175 
175 
200 
200 
250 
250 
500 
500 
January. . . 
76 
173 
58 
14 
11 
4 
4 
0 
0 
1 
0 
0 
0 
0 
February . . 
42 
133 
74 
23 
14 
5 ‘ 
8 
4 
0 
0 
2 
1 
3 
1 
March. . . . 
5 
124 
118 
37 
22 
6 
14 
6 
0 
3 
0 
0 
5 
1 
April .... 
1 
74 
163 
51 
15 
5 
14 
3 
2 
1 
0 
0 
1 
0 
May. 
0 
43 
171 
67 
33 
10 
5 
2 
2 
2 
1 
9 
3 
0 
June .... 
0 
76 
169 
48 
14 
12 
5 
2 
1 
0 
1 
i 
1 
0 
J uly . 
0 
86 
166 
48 
14 
10 
8 
2 
1 
0 
1 
3 
1 
1 
August . . . 
9 
£J 
111 
158 
46 
11 
1 
5 
2 
1 
1 
0 
1 
1 
1 
September . 
9 
139 
108 
37 
14 
5 
9 
3 
3 
0 
0 
0 
3 
0 
October. . , 
22 
168 
91 
25 
17 
8 
5 
4 
1 
0 
0 
0 
0 
0 
N ovember . 
74 
176 
38 
19 
5 
3 
7 
4 
2 
0 
1 
0 
1 
0 
December . 
125 
142 
43 
14 
9 
2 
3 
0 
2 
0 
0 
0 
1 
0 
The step for the six lowest classes is only 12‘5y, answering roughly to 2 r '5 in D, or 
half the step employed in the corresponding tables in my previous paper. For the 
next five classes the step is 25y. The twelfth class has a step of 50y, the thirteenth 
of 250y, while the last class includes the few ranges—-none in D—which exceeded 
500y. It requires a large number of classes to show the distribution satisfactorily 
near the lower end of the scale. Towards the upper end of the scale, the occurrences 
are so few that the employment of a very large number of classes with small steps 
would have been a useless complication. It would, in fact, require a very much 
longer period of years to fix the exact law of incidence for ranges exceeding 200y. 
To facilitate intercomparison, Table LIV. includes results for the whole year from the 
three elements. The 11 years, the four years representing sunspot maximum, and the 
three years representing sunspot minimum are treated separately. Table LIAh 
likewise gives results from the three elements for the three seasons, derived from the 
whole 11 years. 
The results in Table LIV. are shown graphically in fig. 13. The number of days 
in each class was expressed as a percentage of the total number of days included in 
all the classes, and ordinates were drawn proportional to these percentages, due 
allowance being made for the difference between the steps in the earlier and later 
classes. The graphical representation was not carried beyond the 9th class, whose 
superior limit is 150y, because the ordinates for the higher classes would have been 
too short to show satisfactorily, and the irregularities arising from insufficient length 
of period would have been too great. In all the curves the range of greatest 
frequency of occurrence is less than the arithmetic mean range. Also the range of 
most frequent occurrence is always greater for I) than for H, and much larger for 
H than for V. On many days when the D and H curves show large irregular 
