Relative Humidity. 
Ixxxix 
The range of the mean diurnal variation, therefore, gradually increases from the winter quarter till the autumn, 
when it is largest, the ratio of the ranges for the four quarters being as 6 : 9 : 13 : 18 nearly. This varia- 
tion of the range is neither related to the range of temperature, nor to the absolute value of the pressure of 
aqueous vapour. 
Relative Humidity. 
Table 80. — Mean Relative Humidity of the Air for each Month in the Years 1843-6, 
Saturation being equal to Unity. 
Year. 
Jan. 
Feb. 
March. 
April. 
May. 
June. 
July. 
Aug. 
Sept. 
Oct. 
Nov. 
Dec. 
Mean. 
1843 
0-852 
0-873 
0^855 
0-800 
0^845 
0-803 
0^820 
0-850 
0^837 
0-860 
0-904 
©■878 
0^848 
1844 
•935 
•882 
•828 
•775 
•768 
•819 
•808 
•818 
•852 
•848 
•882 
■941 
•846 
1845 
•919 
•857 
•811 
•811 
•831 
•813 
•834 
•835 
•842 
•841 
•875 
■851 
•843 
1846 
•896 
•844 
•836 
■859 
•766 
•736 
•834 
•861 
•874 
•890 
•897 
■901 
•850 
Mean 
•900 
•864 
•832 
•811 
•802 
•793 
•824 
•841 
•851 
-860 
■889 
■900 
•847 
186. Annual Variation of the Relative Humiditi/. — The relative humidity is least in June, and it is greatest 
in December and January ; the three months, April, May, and June, have the least mean, — 0-802 ; the three 
months, November, December, and Januai-y, have the greatest mean, = 0*896. The means for the astrono- 
mical seasons are as follow : — 
Winter, Nov., Dec, Jan., = 0-896 Summer, May, June, July, = 0-806 
Spring, Feb., March, April, = 0-836 Autumn, Aug., Sept., Oct., = 0-8-51 
Year, = 0-847, Saturation being equal to Unity. 
Table 81. — Variations of the Relative Humidity with reference to the Moon's Age and 
Declination, for the Years 1843-6. 
Moon's 
Age. 
1843. 
1844. 
184.5. 
1846. 
Mean . 
After 
Moon 
farthest 
North. 
1843. 
1844. 
1845. 
1846. 
Mean. 
d. d. 
d. d. 
14—16 
-•008 
+ •009 
+ •008 
+ ■011 
+ ■005 
27— 1 
-■010 
-•016 
-■007 
--006 i 
- -010 
17—20 
+ •012 
+ •012 
+ •014 
-■014 
+ ■006 
2— 5 
-■003 
- -003 
--008 
+ -003 1 
- -003 
21—24 
+ •010 
+ •001 
-•010 
-■006 
-■001 
6— 8 
-■001 
-•001 
+ -002 
+ -001 j 
-000 
25—28 
+ •009 
+ •001 
■000 
+ ■022 
+ ■008 
9—12 
- ■OlO 
+ -017 
+ -009 
--016 ! 
■000 
29— 1 
-•005 
-•014 
-■003 
+ ■003 
-■006 
13—15 
+ •013 
+ •012 
--001 
+ •003 
+ ■007 
2— 5 
-•006 
+ ■007 
-■003 
-■020 
-■005 
16—19 
-•025 
-■015 
-000 
+ •024 ' 
-■004 
6— 9 
+ ■002 
-•008 
+ •002 
+ ■013 
+ ■002 
20—22 
+ ■018 
+ ■006 
+ -014 
--005 
+ ■008 
10—13 
-•014 
-•009 
-■005 
-■Oil 
-■010 
23—26 
+ ■017 
-■001 
--007 
--004 1 
+ -001 
187- Variations of the Mean Relative Humidity , luith Reference to the Moon'' s Age and Declination.— 'r]w 
object of this discussion has been already stated, No. 184 ; the results here are considerably more indistinct than 
in the former case ; they agree on the whole, however ; the pressure of aqueous vapour and the relative humidity 
following nearly the same law ; which might be expected if the temperature of the air be supposed not to vary 
with the moon's position. The relative humidity is greatest at and after conjunction ; it is least at and after 
opposition. It is greatest while the moon is ascending from its most southerly position, and least when most 
northerly. (See No. 184 3d). 
