RAIN AND ITS ORIGIN IN THUNDERSTORMS. 



403 



In all the experiments described hitherto the amount of separation has been 

 measured by means of the charge retained on the water. Experiments were now 

 undertaken to see if the charge carried away by the air could be measured. 



The experiment was arranged as indicated in fig. 4. AA was a zinc cylinder 

 8 '5 cm. in diameter and 60 cm. long. Its lower end fitted into a glass taken from 

 a " hurricane lamp," which in turn fitted into another small cylinder as shown at B. 

 Through the bottom of the lower cylinder a glass tube drawn out to an orifice about 

 2 mm. in diameter at its upper end projected into the middle of the glass, and 

 through this orifice a jet of air was passed in a way similar to that described in the 

 previous experiments (see fig. 2, p. 39G). 



ici at, aw " 40 io eo 10 so eo 

 1 m.lro 



FIG. 3. 



FIG. 4. 



From a tube D at the top of the cylinder AA drops of water fell on to the jet of 

 air and were broken up into small drops by the impact. In order to test the air of 

 the jet on which the drops were broken for an electrical charge, an Ebert apparatus 

 was connected to the cylinder AA through a short tube E fixed about 5 cm. above 

 the place where the drops were broken. When the fan of the Ebert apparatus was in 

 action it drew air through holes in the top of the cylinder AA which swept the air of 

 the jet with it through the Ebert apparatus. ' The experiments were made as follows : 



The central cylinder of the Ebert apparatus was charged to a potential which could 

 be read by the divergency of the leaves of the attached electroscope. The air of the 

 jet was then put into action, and a reading of the electroscope taken. The fan was 

 then allowed to draw air through the instrument for 10 minutes, when a second 

 reading of the electroscope gave the loss of electricity due to the natural ionisation of 



3 F 2 



