i5o 



Dr. A. Schuster on 



These three columns are copied from 

 Hittorf s Paper. 



Experiment 



e. 



i. 



A*. 



A/. 



r. 



E. 



I 



*33 



244 



— 



— 



O 



133 



2 



132 



814 



— 



— 



O 



132 



3 



*33 - 5 



1282 



— 



— 



O 



!33"5 



4 



141'S 



3175 



8 



1893 



4230 



132-3 



5 



i5° 



5189 



3-5 



2014 



4230 



132*3 



6 



T 57 



7000 



7 



l8ll 



4250 



J 33'4 



7 



165 



8791 



8 



1791 



4470 



129-7 



8 



i73 



I II92 



8 



2401 



333° 



1397 



In the fourth and fifth columns I have placed the 

 differences Ae and At of electromotive force and currents in 

 successive experiments after the third, the fall of potential 

 in the first three being practically constant. The next 

 column gives r and E calculated by means of the 

 equations 



Ae 

 — . = r 



At 



E = e-ir 

 where for i the arithmetical mean of the currents observed 

 in two successive experiments is taken. 



The last column shews a remarkable consistency ; 

 the first six experiments have given practically identical 

 values for the " back electromotive force," although the 

 current has increased in the ratio of 1 : 34. The mean of 

 the two last experiments also gives the same result, so that 

 increasing the current nearly fifty times we always obtain 

 the same value for E. Such a coincidence, our imaginary 

 experimenter would argue, must prove the correctness of his 

 method, and he would further draw the remarkable conclu- 

 sion that the " true " resistance of his vacuum tube was zero 

 up to a certain current intensity, and then suddenly 

 rose and remained nearly equal to 4,200 ohms. Now 



