16 



Proceedings of the Royal Irish Academy. 



The potential gradient in this quadrangle would be small owing to the high 

 buildings surrounding it, and so the apparatus was well protected from the 

 earth's field. Care was taken to place the apparatus so that no water from 

 the adjoining roofs splashed into it. 



The results were obtained by personal observation between 1st January 

 and 31st August, 19111. The type of rain and on many occasions the size of 

 the drops were observed. No use was made of self-recording apparatus, so 

 that only a portion of the rainfall was obtained. However, the results 

 contained in this paper are probably fairly representative of the year's 

 rain. Tliese results have been divided up into (1) non-thunderstorm rain, 

 (2) thunderstorm rain, (3) sleet, (4) snow and hail. 



1. Non-thunderstorm Enin. 



This kind of precipitation is, of course, far more usual in Dublin than 

 the otliers. During the year 1342 observations* on it were obtained cor- 

 responding to 29,524 c.c. of rain-water. This rain fell on 49 days in 82 

 "falls" or showers. Of these, 987 observations were on positive rain. Tliis 

 is equivalent to 21,714 c.c. of rain-water, or 7o'.') per cent, of the total rain 

 examined. The charge per c.c. varied as under : — 







Posilive Bain. 













No. of obterratioiu, showing charge per c.c. in E.S. units. 



Total 



Average 



Monlh. 











obs. on 



positive 



rain. 



190 



charge 



<1 



•1--2 



•2- -3 



•3- -4 

 18 



•4- -6 

 8 



>-5 



per c.c. 

 in E.8.U. 



Joniiarr, . 



74 



61 



28 



11 



•24 



February, . 



97 



60 



43 



20 



4 



2 



226 



•19 



March, 



71 



17 



8 



6 



4 



9 



115 



•19 



April, 



4 



7 



6 



3 



4 



7 



30 



•63 



May, 



8 



2 



















10 



•05 



June, 



24 























26 



■044 



July, 



15 



1 



1 



3 



2 



2 



24 



■19 



August, 



276 



69 



12 



\h 



1 



5 



367 



•09 



Totals, 



568 



198 



97 



65 



23 



36 



987 



•17 



The remaining 35.5 observations, coi responding to 7810 c.c. of rain-water, 

 or 265 per cent, of the rain examined, were on negatively charged rain. 



' An "observation" means one filling of the tipping-buckot. 



