326 



Mr. John Allen Harker 



[Feb. 9, 



The production of an alternating current of very low frequency 

 is thus rendered possible by the use of some periodic device. In one 

 form of the experiment (shown) the movable electrode is attached 

 to a crank which, rotated slowly by clockwork, performs the necessary 

 displacement of the electrode within the furnace. The ionization 

 currents produced are sufficient to make a nest of small glow-lamps 

 light up brilliantly, the illumination waxing and waning as the mov- 

 able electrode moves in and out. 



20MINS. 40 60 80 100 120 



TIME 

 Fig. 7. — Relation between Ionization Cueeent and Time foe Two 

 New Caebon Electeodes, one Hot, the othee Water-Cooled. 

 No potential was applied. The temperature was risiug for the first fifty 

 minutes, and was afterwards steady. 



We have been able to repeat some of these results with furnaces 

 of a non-electric character. 



In a further series of experiments, various modifications were 

 introduced. I'he two electrodes were replaced by two co-axial tubes 

 which were mounted within the furnace. The central smaller tube 

 was of brass, through which a rapid current of water was sent ; this 

 formed the " cold " electrode. The surrounding larger tube of carbon 

 constituted the hot electrode, and received its heat from the furnace. 



