THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCI 



[SIXTH SER 



JUL Y 1915 



I. The Electricity of Atmospheric Precipitation. 

 By G. C. Simpson, JD.Sc* 



IN recent years a great deal of work has been done 

 with the object or! determining the electrical state of 

 atmospheric precipitation. The results have shown that 

 the whole subject is a complicated one, and different 

 observers do not agree in detail. There are, however, a 

 few outstanding results which may now be taken as estab- 

 lished, and it appears desirable to revise our ideas in the 

 light of these new facts. 



The following are the results which may be taken as 

 having been substantiated by all recent observers f : — 



A. Non-thunderstorm Rain. (Ger. Landregen.) 



(1) Rain is sometimes positively and sometimes negatively 



charged J. 



(2) About 90 per cent, of the rain is positively charged. 



(3) The normal potential gradient is nearly always reversed 



during the rain. 



* Communicated by the Author. 



f I do not propose to discuss the results of individual observers, but 

 give as an appendix a list of all the workers in this subject with refer- 

 ences to their publications. 



% In all probability rain has always some charge and uncharged rain 

 practically never occurs ; but this cannot be stated with certainty until 

 more delicate methods of observation are devised. 



Phil. Mag. S. 6. Vol. 30. No. 175. July 1915. B 



