AT KEW OBSERVATORY, 1890 TO 1900. 
227 
when individual months were considered were 2'34 in November, 1895, and 1*12 in 
June, 1900. 
Inequality ranges from quiet days are generally less, but only slightly less, than 
those from ordinary days. Thus, taking the mean diurnal inequalities for the eleven 
years, the range is 7''90 for the quiet as against 8 /- 03 for the ordinary days, the 
former being thus 98 per cent, of the latter. But the final mean of all the absolute 
ranges for quiet days in Table XIV., viz., 9'*61, is only 77 per cent, of the corre¬ 
sponding mean for ordinary days. The ratio borne by the quiet day to the ordinary 
day absolute range is much larger in summer than in winter, varying from 0'90 in 
June to 0'56 in December. Similarly the ratio borne by the quiet day absolute range 
to that from all days varies from 0'88 in June to 0'52 in December. 
§ 20. The annual variation in the amplitude of the diurnal range presents some 
interesting features which will be most readily recognised on consulting Table XV., 
Table XV.—Monthly Values-of Daily Ranges as Percentages of their 
Arithmetic Mean. 
J anuary. 
r* 
PH 
March. 
April. 
>> 
Cw 
June. 
August. 
O 
O 
05 
m 
October. 
November. 
O 
05 
05 
® I 
G 1 
Inequality 
Quiet days . . . 
54 
63 
110 
130 
135 
131 
128 
134 
120 
93 
60 
43 
ranges 
_ Ordinary days 
59 
74 
107 
129 
126 
128 
125 
129 
113 
92 
64 
54 
' Quiet days . . . 
64 
79 
110 
123 
126 
124 
121 
124 
113 
95 
68 
53 * 
Ordinary days 
81 
94 
113 
113 
110 
105 
107 
109 
109 
104 
83 
72 
_ All days.... 
82 
101 
117 
111 
110 
101 
104 
105 
107 
104 
86 
72 ! 
where the monthly values are represented as percentages of their arithmetic mean. 
For comparative purposes data are given for the inequality ranges as well as the 
absolute ranges. 
The two features which the figures are intended to bring out are : (i.) the reduction 
in the relative importance of the annual variation as we pass from inequality ranges 
to absolute ranges, and from quiet days to ordinary and to disturbed days; (ii.) the 
prominence given to a secondary minimum at midsummer and to maxima at the 
equinoxes in the case of the absolute ranges from ordinary and all days, more 
especially the latter. 
Frequency of Absolute Daily Ranges of Specified Amplitude. 
§ 21. Table XIV. shows how the mean value of the absolute range varies from 
month to month, and from year to year, but this supplies only part of the information 
wanted, For instance, the mean of the absolute ranges for March was 17 per cent. 
2 G 2 
