

ON ELECTRICAL OBSERVATIONS AT KEW, 153 
directly connects the annual period of the electrical tension with that of the 
humidity, and strongly confirms the suggestion already offered, that the high 
tensions at least measure the electrical tension of aqueous vapour. In order 
to illustrate this, the mean annual period of humidity, deduced from five 
years’ observations at the Royal Observatory, Greenwich, is placed in con- 
nexion with the annual period of the electrical tension in the following table, 
in which the electrical tension is expressed in entire divisions of Volta’s elec- 
trometer No. 1, and the humidity in the natural scale, in which complete 
saturation is reckoned as equal to 1000. 
Tas_eE LVII. 
Mean annual periods of electrical tension and humidity. 
Period. | Jan.| Feb.|Mar. April./May.| June.| July. | Aug.) Sept. | Oct. 
Electric..,151|}167| 75} 57 


Now Dec.|/Mean. 

829} 791 | 816 | 845| 874 | 893 /911)| 910) 863 

Humid...| 908 | 894 | 856| 821 | 
TaBLe LVIII. 
Comparison of the excess or defect from the mean of the electric and humid 
annual periods. 

Period. | Jan.\Feb. |Mar. April tay. June.| July. | Aug.| Sept. | Oct.'Nov.| Dec.|Mean. 
— | | | 


+] + + 
Electric..| 84 | 100 10 | 29} 38 | 28 | 38} 34 | 16| 3| 42| 67 



= ~ + 
Humid...) 45 | 31] 7 | 42 | 34] 72 | 47 | 18] 11 | 30 48 47 | 863 

The general correspondence as to the months exhibiting the greatest 
degree of humidity and the greatest 
electrical tension is very percepti- 
ble. It is however to be remarked, 
that the maximum of electrical 
tension does not occur in the same 
= month as that of humidity. In 
Sp Table LVIII., the later occurrence 
fe of the turning-points of the annual 
i period of electricity as compared 
£25 with that of humidity is very 
striking. — 
In the annexed curves (fig. 13), 
the points in which these periods 
correspond as well as those in which 
they differ are rendered very ap- 
parent to the eye. The curve of 
humidity is projected on a scale 
suitable for comparing it with that 
of the electrical tension, 100 divi- 
sions of the natural scale before 
mentioned, or one-tenth of the 
whole, being considered as equal to 
one inch. 
Aunid. [=| + 
Mean annual curves of the electrical tension and humidity. 

