CHAP, iv.] ELECTRICITY AND MAGNETISM. 



261 



movements of a spot of light reflected from a small 

 mirror attached to their needle. Using a water-dropping 

 collector and a Thomson electrometer, Everett made 



Fig. in. 



a series of observations in Nova Scotia, and found the 

 highest + electrification in frosty weather, with a dry 

 wind charged with particles of ice. 



308. Diurnal Variations. Quetelet found that at 

 Brussels the daily indications (during fine weather) 

 showed two maxima occurring in summer at 8 a.m. and 

 9 p.m., and in winter at 10 a.m. and 6 p.m. respectively, 



