180 



Ernst Lecher on the Measurement of 



Experiments with a Statical Charge. 



The arrangement is just the same as in fig. 2 of the 

 previous section, except that a small influence-machine is 

 used in place of the induction-coil. Its terminals were only 

 separated by 0*05 centim., so that the sparks which passed and 

 the potential differences were quite small. The one terminal 

 was put to earth, and the other was connected for about 0'5 

 second with the point r. The adjustment and comparison of 

 the two condensers took place exactly as before. 



For water and petroleum no measurements could be ob- 

 tained by this method, because in this case ocx' acted as an 

 earth-connected screen. In order to bring the needle to zero, 

 I had to remove E' to an infinite distance from E, so great 

 was the conduction due to the small amount of water which 

 the petroleum contained. 



For the other substances, the measurements are given in 

 the following table : — 





Ebonite 

 (0-7164 

 centim.). 



Glass 

 (0-8797 

 centim.) 



Two glass 



plates (0-4338 



centim.). 



With the dielectric 



With air 



1-5820 

 1-0090 



2-0640 

 1-4863 



2-4885 

 1-6150 



19820 

 1-1062 



1-8631 

 1-4330 



1-9942 

 1-5638 





Difference 



0-5730 



0-5777 



0-8735 



0-8758 



0-4301 



0-4304 





The corresponding dielectric constants are : — 



Plate Glass. 

 4-67 



Solinglas." 

 4-64 



Ebonite. 

 2-64 



Synopsis of Results. 



Collecting the results obtained by the three methods, in all 

 of which high potentials are used, we find : — 



