Electricity of Atmospheric Precipitation. H 



to expect that the electrical effect with snow is very large, 

 probably much larger than can be obtained, by splashing 

 water, and this would explain the high charges observed. 

 But a snow-flake is much less suitable than a raindrop for 

 causing a large separation of electricity, for its downward 

 movement relative to the air is very small, hence much of the 

 electricity separated joins up again. This probably accounts 

 for the absence of thunder and lightning during snowstorms. 



In Simla we have much thunder and lightning at the 

 beginning of snowstorms, but so far as my observations go,, 

 during the thunder and lightning the snow is accompanied 

 by much small soft hail. The latter, falling through the 

 snow, becomes highly charged by impact, and its rapid rate 

 of fall gives the condition for a large separation of electricity. 

 This no doubt accounts for the large excess of positive charge 

 on the snow investigated at Simla. 



It is questionable whether thunder and lightning ever 

 accompany a pure snowstorm. Certainly they do not occur 

 in polar regions, and are very rare during snow in the 

 winter in Europe. More observations will probably prove that 

 violent ascending currents producing soft hail are necessary 

 for thunder and lightning to accompany a snowstorm. 



The latter part of this paper may be summarised by 

 stating how each of the results of observation given on 

 pages 1-3 is accounted for by the theory. 



(1), (4), and (8). Tho process described gives a positive 

 charge to the precipitation and a negative charge to the air, 

 thus accounting for the positively charged precipitation. 

 The air carrying its negative charge may get removed from 

 the place of origin, and then precipitation formed in it will 

 start with a negative charge. If this falls to the ground 

 without becoming charged positively, it will appear as 

 negatively charged precipitation. 



(2) and (5). The chief fnctor at work gives rise to a 

 positive;charge on the precipitation and a negative charge on 

 the air. As the precipitation falls to the ground, while the 

 air tends to prevent the negative charge reaching the ground, 

 the precipitation as a whole will be positively charged. 



(3), (7), and (11). The changes in the potential gradient 

 result directly from the large separation of electricity, and 

 from the fact that the charge carried to the ground by the 

 precipitation completely masks the small permanent charge 

 normally on the ground. 



(2) and (/>). During quiet non-thunderstorm rainfall 

 there is not so much breaking of drops as in thunderstorms 

 with their violent ascending currents, hence the charges are 

 less. At the same time the condition^ are more suitable for 



