90 Proceedings of the Royal Irish Academy. 



Electric Charge on Snow and Hail. 



A few short showers of snow and hail occurred during the period covered 

 by these observations. The apparatus is not specially suited for dealing 

 with snow ; but the charge could be accurately measured and the quantity of 

 snow estimated at the end of the shower by collecting it and washing out the 

 receiver with warm water. Five showers of snow occurred. In each case it was 

 negatively charged. The average charge per gramme was 2'8 electrostatic units. 



The potentials accompanying snow-showers are abnormal. On three of the 

 five occasions on which snow fell the showers were quite heavy, although 

 lasting for only a short time. Before the snow began to fall the electroscope 

 giving the potential showed the uoimal positive value, which for the point 

 in question was about 100 volts. On the arrival of the snow the potential 

 changed quite quickly to a very high negative value outside the range of the 

 electroscope, but which was measured by a less sensitive electroscope when 

 the other showers occurred, and negative values as high as 2500 volts were 

 found. This high negative potential was maintained during the showers, but 

 fell away suddenly when the snow ceased, and the electroscope recorded a 

 normal positive value as before. 



We have stated that the snow observed was negatively charged ; but one 

 exception should be noted. During one shower the charge changed to 

 positive for a period of less than a minute. It may be noted that Simpson 

 usually found snow to be positively charged. 



Only one shower of hail occurred, and it was positively charged, the 

 average charge per gi-amme being approximately two electrostatic units. 

 On two other occasions showers fell which consisted of mixtures of snow 

 and hail. These showers gave further evidence that the snow was negatively 

 charged and the hailstones positively charged. Thus when the hailstones 

 visibly predominated, the charging of the receiver was positive, and vice versa. 

 An excess of negative was recorded on both occasions; 7'6 units for 80 

 grammes in one shower, and 8-4 units for 200 grammes in the other. 



Summary. 



The results in this paper may be summarized as follows : — 



1. Of the rain tested 88'2 per cent, was positively electrified and the 

 remainder negatively ; of the electricity collected 93'5 per cent, was positive 

 in sign. 



2. Eain consisting of very minute drops was always negatively charged. 



