18 



much closer in fig. 3 than in fig. 2, even when large poten- 

 tial differences are applied between the electrodes. The re- 

 sults with the gauze positive are in all cases larger than with 

 the gauze negative. Also, the number of ions reaching the 

 central electrode in a given time decreases for any given value 

 of potential difference between the cylinders, as the distance 



lh£arth 



hap 



From Centre C^u^e 

 ho ^ 

 flectromehr. 



R Sulphur 

 P. TopQdUjt 

 Q Middle. .. 

 R Bottom .. 



Fig. 4. 



between the gauze and the end of the central electrode is in- 

 creased. When, therefore, even very large potential differ- 

 ences are maintained between the electrodes, the number of 

 ions which reach the central electrode in a given time may 

 give a very false measurement of the number of ions which 

 actually reach the gauze in that time. 



