Edison Effect in Glow Lampi 



69 



Table No. 6. Lamp No. 3. Elliott Galvanometer. 



Table showing the relative values of the potential-difference 

 between cylinder Y and the positive electrode for good 

 and imperfect vacua in the case of lamp No. 3. 



Working 



volts of the 



lamp. 



Very high vacuum in the lamp. 



Imperfect vacuum in the lamp. 



Watts per 



candle-power 



taken up in 



carbon. 



Volts between 



cylinder Y 



and positive 



electrode. 



Watts per 



candle-power 



taken up in 



carbon. 



Volts between 



cylinder Y 



and positive 



electrode. 



40 



6-75 



2-02 



9-1 



4-17 



41 



575 



2-89 



7-9 



7-25 



42 



5-30 



362 



6*5 



8-39 



43 



4-90 



4-54 



5-9 



9'80 



44 



4-50 



6-08 



4-3 



11-96 



45 



4-15 



7-50 



4-0 



13-76 



46 



3-84 



9-25 



37 



15-08 



47 



355 



10-33 



3-4 



1621 



48 



3-30 



13-2 



3-2 



18-28 



49 



3-07 



16-3 



30 



22-05 



40 



2-90 



18-4 



2-8 



22-99 



51 



2-74 



21-8 



2-6 



23-93 



52 



2-58 



24-4 



2-4 



28-26 



The imperfection of the vacuum is indicated by the higher 

 watts per candle-power absorbed at low voltages, and we 

 see that at any given working pressure the potential-difference 

 between the positive electrode and the cylinder Y embracing 

 the top of the negative leg is greater when the vacuum is 

 imperfect than when it is very good. The presence of residual 

 air tends to bring down the potential of the embracing 

 cylinder more nearly to that of the carbon at the point adja- 

 cent to it. 



§ 8. Experiment 5. — A series of observations was next 

 made in which the potential-difference between the middle 

 plate and the positive electrode was determined by the aid of 

 a condenser. If a condenser of capacity C in microfarads is 

 charged to a potential of V volts and discharged through a 

 ballistic galvanometer, we can determine the ballistic constant 

 of the galvanometer. A second observation of a like nature 



