196 



Dr. Everett on Atmospheric Electricity. [Dec. 5, 



secondary maximum between 20^ and 21''. At Windsor, on the other 

 hand, the mean potential about 9^^ was in every month, without excep- 

 tion, less than at the other principal times of observation, viz. about 21'' 

 and 14^ 



The following Table shows the ratio of the mean monthly to the mean 

 annual potential for the whole series of observations at both places : — 



Kew. 



1862 



June 

 July 

 Aug. 

 Sept. 

 Oct. 

 Nov. 

 Dec. 

 Jan. ] 

 Feb. 

 March 

 April 

 May 



Oct. 1862 

 Nov. „ 

 Dec. „ 

 Jan. 1863 

 Feb. „ 

 March „ 

 April „ 

 May „ 

 June „ 

 July „ 

 Aug. „ 

 Sept. „ 



•770 



June 



1863 



.770 



July 



jj 



•836 



Aug. 



»j 



•845 



Sept. 



J) 



•981 



Oct. 



JJ 



1-600 



Nov. 



JJ 



M88 



Dec. 





P033 



Jan. 



1864 



1-333 



Feb. 



JJ 



M60 



March „ 



•920 



iVpril 



JJ 



•672 



May 



JJ 



Windsor, N.S. 





•832 



Oct. 



1863 



•766 



Nov. 



JJ 



1-010 



Dec. 



JJ 



1-057 



Jan. 



1864 



1-432 



Feb. 



JJ 



1-396 



March „ 



1-023 



April 



JJ 



•796 



May 



JJ 



•720 



June 



JJ 



•755 



July 



JJ 



•952 



Aug. 



JJ 



•985 







•643 

 •685 

 •854 

 1-000 

 1-390 

 1-460 

 1-226 

 1-263 

 r375 

 •831 

 •549 



1-033 

 -949 

 1-110 



1-416 

 1026 

 •985 

 •799 

 -885 

 (-862) 



The last step in the reductions consisted in expressing the variations, 

 both diurnal and annual, at Kew, and tbe annual variations at Windsor, by 

 the first two terms of an harmonic series. 



In the case of the diurnal variations at Kew, the amplitudes of the two 

 terms were nearly equal, but the epoch was much more uniform in its 

 values (whether in comparing one year with the other or in comparing one 

 month with another in the same year) for the second term than for the 

 first. 



In the case of the annual variations, the amplitude of the second term at 

 Kew was almost inappreciable, while at Windsor it was greater than that 

 of the first term. 



