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 vai-ia- 

 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 



0-878 



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 Humidity, — 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 January, have the greatest mean, = 0-896. The means for the astrono- 

 mical seasons are as follow : — 



Winter, Nov., Dec, Jan., = 0-89 6 Summer, 



Spring, Feb., March, April' = 0-836 Autumn, 



Year, = 0-847, Saturation being equal to Unity 



May, June, July, 

 Aug., Sept., Oct., 



= 0-806 

 = 0-851 



Table 81. — Variations of the Relative Humidity with reference to the Moon's Age and 



Declination, for the Years 1843-6. 















After 













Moon's 













Moon 













Affe. 



1843. 



1844. 



1845. 



1846. 



Mean . 



farthest 



1843. 



1844. 



1845. 



1846. 



Mean. 















North. 













d. d. 













d. d. 













14—16 



-•008 



+ •009 



+ •008 



+ •011 



+ •005 



27— 1 



-•010 



-•016 



-•007 



-•006 



-•010 



17—20 



+ •012 



+ •012 



+ •014 



-•014 



+ •006 



2— 5 



-•003 



--003 



--008 



+ •003 



-•003 



21—24 



+ •010 



+ -001 



-•010 



-•006 



-•001 



6— 8 



-•001 



-001 



+ •002 



+ •001 



•000 



25—28 



+ •009 



+ -001 



•000 



+ •022 



+ •008 



9—12 



-•010 



+ •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 



+ -001 



187. Variations of the Mean Relative Humidity , with Reference to the 3Ioon's Age and Declination. — The 

 object of this discussion has been already stated. No. 184 ; the results here are considerably more indistinct tlian 

 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 Zd). 



