MH'mci.lani) and Gilmouk — The ElcHric Charge on Ruin. 19 



rain occuiiL'd nu a .sitiLjlc occasion. IL will also be seen that the highest 

 charges per c.c, both positive and negative, were obtained in Maieh and 

 April, generally in short showers. A positive charge of 10"1 E.S.U. per c.c. 

 was got on a little shower on March 27th, and o'2 E.S.U. per c.c. on a 

 shower on April 14th, while both positive and negative charges of 1 to 3 

 E.S.U. per c.c. were obtained on several occasions in April. 



On almost every occasion the times between successive discharges of the 

 tipping-bucket were noted by means of a stop-watch, so that it is possible to 

 investigate the I'elation between the charge and the rate of fall, as well as 

 the vertical current per square cm. due to the rain. 



Simpson^ and Baldit" found the highest positive and negative charges 

 associated with light rain, while M'Clelland and Nolan' found the highest 

 cliarges connected with heavy rain. In the case of positively charged rain 

 the present investigation seems rather to support M'Clelland and Nolan, as 

 will be seen from the following tables, showing the number of observations 

 obtained for different times of discharge of the tipping-bucket and the 

 corresponding average charges per c.c. The different times of discharge of 

 the tipping-bucket were taken as being more convenient for the purposes of 

 calculation than the rate of fall. The corresponding rates of fall are given 

 afterwards. 



' Simpson, Phil. Trans. A, ccix (1909). 



^ Loc. cit. 



3 M'Clelland and Nolan, Roy. Irish Acad. Proc. xxi, A (1912). 



