66 



Proveediiiyfi uj tlie lioijal Irish Acadciiuj. 



the " large rain " is rather of a showery or temporary nature. It would appear 

 also to come generally from low-lying clouds, whereas the highly charged 

 type appears to come from a greater height. 



" Fine Rain." 



It was pointed out in the previous paper that rain consisting of exceedingly 

 small drops was frequently noted and found to be always negatively charged. 

 We have had few cases of this extreme type during the winter months. When 

 it occurred it was, as before, negatively charged. Owing to the very small 

 precipitation of water during this type of rain, only a few observations of the 

 charge per c.c. were made ; the average value of the charge was about O'l 

 electrostatic unit per c.c. 



Current in Amperes per sq. cm. 



We may express the charge iDrought down by the rain as a current per 

 sq. cm. of the earth's surface. As we have previously pointed out, owing 

 to the way in which the receiver is shielded by a surrounding cylinder it 

 gets only a fraction of the total rainfall. The correction to be applied will 

 vary with the velocity of the wind. By comparison with an unshielded rain- 

 gauge we have estimated the correction, and it is believed that the following 

 tables are sulastantially correct. They show the number of times that values 

 of the current lying Ijetweeu certain limits have been observed : — 



Table III. 

 A. — Positive Rain. 



Current in Ani|ieres X 10"'° per sq. cui. 



MoveDiber, 



December, 



January, . 



February, 



March, 



May, 



Totiil, 



75 

 34 

 104 

 67 

 49 

 19 



