McClI'Xland ami Nolan — The Electric Charge on Ruin. 71 



the atmosphere, little work has been done on the subject of the large ions 

 shown to exist by Lange^in. The larger ions are almost certainly of 

 much greater importance than the small ions as regards condensation and 

 atmospheric electricity in general. On these two subjects work is in 

 progress, and we hope to publish fiu'ther results at an early date. 



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

 (1) Of the rain tested, 82-6 per cent, was positively charged and the 

 remainder negatively ; of the electricity brought down by the rain, 76'9 per 

 cent, was positive. 



(2} A distinction is made between different types of rain : — 

 (a) A type which seldom occurs diu'iug winter and of which the drops 

 are relati\'ely lai-ge, is distinguished by the higli charge it carries, 

 the average value being from 1 to 2 electrostatic units per c.c. 

 The charge on this type is nearly always positive. 

 (h) A less highly charged tji^e which occurs throughout the year, aud 

 especially during the winter months. The drops are relati^'elj' 

 smaller, and differ in size. The average charge per c.c. is from 

 0-1 to 0-2 electrostatic units, and the sign of the charge is usually 

 positive. 

 (c) Eain consisting of exceedingly minute drops is sometimes observed, 



and the charge is small and always negative. 

 (3) Tables are given showing the distribution of charge per c.c. between 

 certain limits. Other tables, in calculating which the rate of fall of the rain 

 is taken into account, show the current in amperes per sq. cm. of the Earth's 

 surface. 



(J:) Snow was obser\-ed with charges of both signs; the charge was 

 negative when, the flakes were small, and a positive charge was observed 

 in the case of a shower of large flakes. The charge on snow per gramme was 

 high, and the snow was accompanied by high values of the potential gradient. 

 Hail was observed on only two occasions, and it had a positive charge. 



All the observations recorded in this paper were made during what may 

 be called normal electrical conditions. We had no opportunity of obser^•ing 

 the electric charge on rain during a thunderstorm. 



