ox “QUIET” DAYS DUKINO THE ELEVEN YEAKS 1890 TO 1900, ETC. 
375 
mean inequality for the year. In fact, the data from March give a better general 
idea of the phenomena than those from any other month. 
§ 28. To fiicilitate comparison of the law of variation throughout the year of the 
range and the sum of the 24 differences in the diurnal inequalities of 1), 1, H, and V, 
T give a synopsis of the whole of the data in Table XVIl 1. Here each quantity dealt 
witli is expressed as a percentage of its mean value for the 12 inontlis. T1 lis enables 
us to see more readily points of agreement and difference. It will he observed that 
there is a close resemblance between the annual variations in D, I, and H, and that 
the mean of the results from these three eleinents for tlie raime and for the sum of 
O 
the 24 differences are very similar. On the whole, the sum of tlie 24 differences has 
the more accentuated annual variation. 
The annual variation seems somewhat greater in V than in the other elements, the 
maximum in May being exceedingly prominent. 
Table XVI11.--Monthly Relative Values. (100 = Mean from 12 Months.) 
Ihinge. 
Sum of 24 differences from mean. 
Mean 
Mean 
D. 
1. 
11. 
V. 
of 
D. 
I. 
H. 
V. 
of 
1), I,H. 
D, 1, H. 
Jaiiiuiry . 
51 
62 
54 
35 
55 
57 
49 
40 
44 
49 ' 
Felu'uary . 
59 
64 
59 
55 
61 
74 
61 
54 
57 
63 , 
March .... 
110 
87 
91 
108 
96 
106 
88 
92 
102 
96 ' 
April .... 
132 
118 
127 
136 
126 
120 
123 
132 
132 
125 
May .... 
13G 
130 
135 
170 
134 
128 
132 
143 
174 
134 
June .... 
132 
128 
137 
143 
132 
136 
134 
140 
137 
137 
July .... 
127 
130 
136 
153 
131 
128 
135 
144 
154 
136 
August 
137 
136 
134 
126 
136 
132 
139 
138 
126 
136 
September . . 
122 
125 
123 
110 
123 
117 
121 
120 
117 
119 
October . . . 
93 
99 
96 
82 
96 
94 
105 
102 
83 
100 
X^ovember 
59 
80 
71 
50 
70 
64 
78 
66 
45 
69 
December . . 
42 
40 
37 
31 
40 
44 
35 
29 
30 
36 
§ 29. Figs. 2 to 7 should give an adequate pictorial idea of the general character 
of the diurnal inequality in individual elements. 
A more complete idea of the phenomenon as a whole can Ije obtained fiuin two 
other types of curves. The first type, commonly known as the “ vector diagram,” 
has been used by Lloa'D, Aira' and others. It represents the variation throughout 
the 24 hours of the disturbing force to which ]nay be ascribed the changes in the 
horizontal component of magnetic force. The radius vector from a fixed point 
represents the horizontal component of the disturbing force in magnitude and 
direction. When inequalities for N and W have been calcidated, the simplest w ay 
to draw the diagram is to take the hourly values of tlie N and W inecpialities as 
