14 Proceedings of the Roi^al Irish Academy, 



He summarizes the outstanding results of their work as follows : — 



A. — Non-th xmderstoiin liatii. 



1. Eaiii is sometimes positively and sometimes negatively charged. 



2. About 90 per cent, of the rain is positively oharged. 



3. The normal potential gradient is nearly always reversed during the 

 rain. 



B. — Thunderstwm Rain. 



4. The precipitation is sometimes positively and sometimes negatively 

 charged. 



5. Moi-e positive than negative electricity is brouglit down by tlie 

 precipitation. 



6. The charges per unit mass of tlie precipitation and the vertical 

 electrical currents produced by its fall are much larger than wiili non- 

 thunderstorm rain. 



7. The potential gradient undergoes large and rapid changes of sign, and 

 on the whole the potential gradient is more often reversed than not. 



C. — Snow. 



8. Snow is sometimes positively and sometimes negatively charged. 



9. In Simla positive electricity was in e.xces8, while in Potsdam an 

 excess of negative electricity was observed. 



10. A given weight of snow may be more highly charged tiian the same 

 amount of rain, even in a thunderstorm. 



11. High values of tlie potential gradient, both positive and negative, 

 occur during snowfall. 



DirtVrent observers, however, do not agiee in details, and more work on 

 the subject is needed. 



The work described in this paper was done at University College, Dublin. 

 The apparatus employed was essentially the same as that used byM'Clelland 

 and Nolan.' The receiving ve-ssel, A, was made of zinc, conical-shaped, 

 81-3 cm. in diameter. Attached to it, and in metallic connexion with it, 

 was a tipping-bucket. B, arranged to discbaige itself when 22 c c. of water 

 had run into it from the receiving vessel. This part of the apparatus rested 

 on a tripod, from which it was insulated by a parafiin wax ring. The whole 

 was enclosed in a cubical wooden box, measuring about 1 metre each way, 

 with a zinc top, sloped, so as to throw off the rain which fell on it. A circular 



' H'Clulland and Nolan, \loy. Irish Acad. Froc., vol. xxix, A. Feb., 1912. 



