Electricity at the Kew Observatory. 123 



chronological, but in descending order of the voltages observed at 

 station A. In all the tables the humidity of saturation is taken as 

 100. 



21. I have divided the results in each of the previous eight 

 tables into two groups, according to the order of voltages at station A. 

 The two groups are equal in number of constituents, except as 

 regards Table XV, where, following a marked line separating the 

 voltages, I have included six in the first group, and seven in the 

 second ; and Table X, where I have included four in the first group, 

 and three in the second. In tlie last-mentioned case, the best line 

 of demarcation is doubtful, and, on account of this, and the small 

 number of constituents, little weight can be attached to the results. 



It may seem arbitrary to determine the groups by reference "to 

 station A exclusively. It is, however, the station least influenced 

 by buildings, and best fitted for accurate readings, while B is the 

 worst. Also it will be seen that if one had adopted either C, D, or 

 E as the standard station, or had taken a mean from all the stations, 

 whilst the order of the constituents would in some tables have 

 been considerably affected, the groups themselves would have suf- 

 fered little or no change. 



Table XVII gives the mean potentials at station A for each group 

 in the several series of observations, with the corresponding mean 

 values of the meteorological elements. 



