M'Ci.Ki.LANi) AND GiLAfoiiR — The FAcclvlc Chnrije. on Ihiin. lo 



opening was cut in this zinc, the edge nf which wii.s tuiiinl up Id a height of 

 al)out lialf a centimetre. 



On tlie top of this opening was placed a zinc cylinder, 91 cm. high and 

 91 em. in diameter. All this zinc and wooden bo.\ wei'e connected to earth. 

 The receiving vessel was connected to a Dolezalek electrometer by a copper 

 wire, enclosed in earthed metallic tubes, from which it was insulated by 

 paraffin wax. The capacity of the electrometer, receiving vessel, and con- 

 nexions was 0003 microfarads. The sensitivity of the electrometer was 

 about IGOO mm. divisions per volt. When making mea.'^urements on the 



Fio. 1. 



rain it was found necessary to add to the electrometer capacities varying 

 from -001 to '5 microfarads. The charge on the rain was calculated from 

 the observed increase in potential of the apparatus, and the capacity. The 

 discharge of the tipping-bucket was generally heard, bui, was always notified 

 by its automatically earthing the apparatus. As a precaution, the apparatus 

 was earthed independently at each discharge of the tipping-bucket. 



The apparatus was set up in a small quadrangle at the back of the college. 



[3«] 



