62 Proceedings of the Royetl Irish Academi/. 



made daiiiig this series of expeiiments. In practically all cases, however, 

 the time of each discharge of the tipping-bnckets was noted, so that it is 

 possible to calculate the rate of lainfall at any time, and also to express 

 the charge of the rain as a current per square centimetre of the earth's 

 surface, 



Sestdts of Observations. 



During the eight mouths over which this second series of observations 

 extended, rain was examined on sixty-eight separate oc-easions : on eighteen 

 of these occasions only was there an excess of negative electricity recorded ; 

 on fifty occasions the positive electricity was in excess. 



The total amount of rain collected in the apparatus was 22,6-50 c.c, in 

 quantities of 30 c.c. each : of this amount 18,720 cc, or 82"6 per cent., were 

 positively charged, and the remainder negatively. 



This amount of water would corre.spond to a rainfall of about 4*6 cms. 

 if falling directly into the receiving vesseL The vessel was, however, 

 surrounded by a cylinder rising to a considerable height above it, as 

 described in the previous paper; and as the lain often fell at a large 

 angle to the vertical, the actual rainfall of which we have examined samples 

 is greater than 4-6 cms. 



In the previous series of observations, we examined 5113 cc. of positive 

 I'ain and 682 c.c of negative rain. If we combine the two sets of obser- 

 vations, we get 28,44.5 cc. of rain, of which 23,83.3, or 83-8 per cent, are 

 positive. 



As to the charge on the rain we find in this series of expeiiments that 

 7.112-1 electiostatic units of positive electricity have been brought down as 

 against 2,131-7 units negative. The positive, therefore, forms 769 per cent 

 of the total electricity carried down by the rain. In the previous experiments 

 we had 4151'4 electrostatic units of positive charge, and 2897 units negative. 

 Combining these results as before, we find a total of 11,263'5 units positive 

 and 2,421-4 units n^ative. Thus the positive forms 82'3 per cent of the 

 whole. We believe, however, that the results of the present set of observations 

 considered by themselves give a better idea of the general average for the 

 normal year. 



That there are considerable variations in the electrical properties of 

 the rain at diSerent times of the year will be seen from the following 

 table, which sets forth a summary made for each month. It furthermore 

 shows the continued predominance of the pc^tively charged redn. 



.Thelowne^ of tiie values of the charge per cc, during the winter months, 

 as compared with the values got in March and May, is readily observed. 



