1912] 



on Very High Tmnperatures. 



325 



Fig. 5 exemplifies the exponential relation between temperature 

 and current for a 1 cm. gap and an applied potential of 2 volts. The 

 dotted straight line was plotted to axes of temperature and logarithm 

 of current. 



The magnitude of the currents made it evident that in spite of 

 the high pressure the atmosphere of the furnace was ionized to an 

 unusual degree at high temperatures, and we were led to investigate 

 the effect of temperature alone. The battery was accordingly cut out 



5mi«s 10 15 20 25 30 35 



TIME 

 6. — Rei-ation between Ionization Current and Time with a 

 Steadily Rising Temperature. The " cold " electrode was water- 

 cooled ; the hot electrode was of new carbon. No potential was applied. 



and one of the two carbon electrodes was mounted on a sliding 

 carriage so that it could, at will, be moved in or out of the hot part 

 of the furnace, i.e. away from tlie fixed electrode or back towards it. 

 The movable electrode would thus be temporarily cooler than the 

 fixed electrode which remained steadily in the furnace. The ammeter 

 in the circuit indicated a current which amounted to 2 milliamperes 

 at 1400° and nearly 2 amperes at 2500° ; the cooler electrode was 

 the positive one. The currents died away when the two electrodes 

 attained the same temperature. 



z 2 



