EATIO OF ELECTROMAGNETIC TO ELECTROSTATIC UNIT 273 



effect. I satisfied myself by suitable experiments that the error from 

 this cause might be neglected. 



The method of experiment was as follows: The store of electricity 

 was contained in a large battery of Leyden jars. This was attached 

 to the electrometer. The reading of the potential was taken, the 

 handle of the discharger was turned and the momentary swing observed 

 and the potential again measured. The mean of the potentials ob- 

 served, with a slight correction, was taken as the potential during the 

 time of discharge. This correction came from the fact that the first 

 reading was taken before the connection with the condenser was made. 

 The first reading is thus too high by the ratio of the capacities of the 

 condenser and battery and the mean reading by half as much. Hence 

 we must multiply d by 1 F where F= -0013 for first ball of con- 

 denser and -0008 for other. This will be the same for 1 or 5 dis- 

 charges. From 10 to 20 observations of this sort constituted a set, and 



the mean value of -, which was calculated for each observation sepa- 

 rately, was taken as the result of the series. 



Before and after each series the times of vibration, t and T, and the 

 readings, /9 and a, were taken. The logarithmic decrement was ob- 

 served almost daily. 



EE STILTS 



The table on the following page gives the results of all the observa- 

 tions. 



These results can be separated according to the number of discharges 

 as follows: 



1. 



300-59 

 300-17 

 296-72 

 297-84 

 298-90 

 298-57 

 299-05 

 300-80 

 296-56 



298-80 298-48 297-26 29715 296-69 

 18 



