436 Mr. H. A. Wilson : Determination of the Charge 



In an experiment made in this way the following numbers 

 w T ere obtained : — 



Distance between the disks 1'0 cm. 

 P.D. = 2000 volts. 



Time of Fall. 



X=+6-7. X=-6-7. 



sees. sees. 



(1) 18-4 (2) 21-6 



(3) 25-7 (4) 27-1 



(5) 19'4 (6) 22-4 



(7) 24-2 (8) 27-8 



- (9) 27*0 (10) 32-6 



Mean... 22-94 Mean... 26*3 



These numbers give 



v 2 = 00436 — 

 sec. 



t> 3 =0-0380 — 



sec. 



3-1 xl0-\? 



Also 



2* X 



O 2 -n0 {v 2 +^)K 



so that 



e = 2-6xl0- 10 E.S. units. 

 and 



m=31 x 10- 9 x (J^Y =2-5 X lO-^gram. 



As already mentioned the cloud soon begins to evaporate 

 after it is formed, so it is important to get the measurement 

 of its rate of fall over as quickly as possible. It was, there- 

 fore, found most satisfactory to use the rates of fall with 

 X = and with X positive, making the rate of fall greater 

 than when X = 0. 



In making a series of measurements an observation wdth 

 X positive was always made as quickly as possible after one 

 with X = 0, in order that the strength of the rays and other 

 conditions should be as nearly as possible the same in both 

 cases. Although the individual observations in a series, say 

 with X = 0, often vary a good deal, yet there is usually a 

 corresponding variation in the observations with X positive, 

 so that the value of e obtained from the mean results for the 



