RAIN AND ITS OEIGIN IN THUNDERSTORMS. 399 



This result is of the same order of magnitude as that found by LENARD for single 

 large drops breaking on a metal obstacle, the charge produced by each drop in these 

 experiments being even larger than that found by LENARD in his experiments. 



Experiments were next undertaken to investigate the extent to which the process 

 is affected by any charge already on the drops, for it is quite conceivable that charged 

 drops might behave quite differently from uncharged drops. For these tests the 

 apparatus already described was adapted. It was only necessary to connect the 

 cylinder C to a battery, so that each drop which fell from the funnel had a definite 

 charge induced on it, and carried it away with it on its fall. The charge carried by 

 each drop was found by catching the drops in the small box shown dotted in fig. 2. 

 The box was then removed, and the charged drops broken up on the air jet. The 

 difference between the total charges measured, with the same number of drops in 

 each case, indicated the extent of charging due to the breaking up on the air jet. 



The following gives a typical experiment, in which distilled water was used and 

 each drop carried a positive charge : 



TABLE XI. 



Drops caught in little box. 



No. of drops 



Deflection 



100 200 300 400 500 



20-0 17-3 14-3 11-4 8'5 5-7 



Total deflection = 14'3 cm. = +33'5 volts. .'. Charge per drop = 19'5 x 10~ 3 els. unit. 



The small box was then removed, and the drops broken on the air jet. 



TABLE XII. 



Drops broken on air jet. 



Total deflection = 17'5 cm. = 41O volts. .'. Charge per drop = 23'9 x 10~ 3 els. unit. 



Prom these two experiments we find that drops originally positively charged to 

 19'5XlO~ 3 els. unit have had this charge increased to 23'9xlO~ 3 els. unit when 

 broken up on the air jet, the increase being 4'4x 10~ 3 els. unit per drop. 



