M'Ci.KM.AND AND GiLMouR — Tlic Eleclvic Charge on Rain. 29 



that of the smallest raindrop; but the stains left by them were more irregular 

 than those of the raindrops. 



Very regular stains, which could be accurately measured, were left by 

 the hailstones. The small negatively charged hailstones varied between the 

 same limits as the raindrops, generally less than 2'5 m. gms. in weight. The 

 large hailstones were very much larger than this. On one occasion some of 

 them weighed about 50 m. gms., and many between 30 and 40 ni. gms. 



SUMMAEY. 



1. liain was never found uncharged. 



2. Of non-thunderstorm rain tested — 



(«) 73'5 per cent, was positively charged. 

 (h) 84 per cent, of electricity brought down was positive, 

 (c) Average positive charge per c.c. = '21 E. S. units. 

 Average negative charge per c.c. = '08 E. S. units. 

 ((J) Average vertical current due to positive rain = r6 x lO"" amps. 



per square em. 

 Average vertical current due to negative rain = '5 x 10''* amps. 



per square cm. 

 (c) Eain consisting of droplets smaller than '08 x 10"' c.c.s was always 



negatively charged. 

 (/) No general relation was found between charge and size of drops. 



3. Thunderstorm rain (two storms examined) — 



{a) 54-2 per cent, positively charged. 



(&) 50-3 per cent, of electricity brought down was positive. 



{c) More highly charged than ordinary rain. 



4. Hail and snow — 



(ft) Snow sometimes positively charged ; excess negative. 

 (6) Small hailstones always negatively charged, 

 (c) Large hailstones always positively charged. 



{d) Charge per c.c. higher than on rain ; often higher than on thunder- 

 storm rain. 



R.I. A. PUOC, VOL. XXXV, SECT. A. [4] 



