under the Influence of the Electric Discharge. 369 



tine was somewhat different, the following amounts of heat 

 were obtained for the positive discharge at the pressures p, 

 when the spark-lengths and 10 millims. were interposed: — 



V 



X 



0-6 



4-3 



12-8 



25-6 



35 



90 



166-4 



567 







0-253 



0-082 



0-072 



0-088 



0-10 



0-16 



0-30 



0-52 



1-17 



10 



1-34 



0-84 



0-52 



0-56 



0-69 



0-80 



0'81 



1-10 



1-77 



759 

 1-30 



2-2 



The number of discharges when no spark was interposed 

 was 



p ... 730 400 160 90 30 



20 



40 120 220 about 700 



increasing now up to very low pressures and then decreasing. 



With a spark-length of 10 millims. interposed the number 

 z was about 13 for all pressures. 



A comparison of these numbers shows that the amounts of 

 heat corresponding to the same quantity of electricity transmitted 

 are by no means inversely proportional to the number of dis- 

 charges. Thus the number of discharges z and z 10 , and the 

 quantities of heat w Q and M7 10 , with the spark-distances 

 and 10 millims., and at the pressures p, are somewhat as 

 follows : — 



p 



z : z 10 . 



w : w 10 . 



180 

 90 

 30 



10: 1 

 17:1 

 50:1 



1 :2 

 1:3 

 1 :6 



This may also be seen in another way. Whilst the amounts 

 of heat between 759 and 4*3 millims. pressure without spark 

 sink from 1*3 to 0*072, or to -^, with spark interposed they 

 sink only from 2*2 to 0*5 — that is, only to \. 



We may conclude from these facts that, when a spark is in- 

 cluded in the circuit, the discharge of the whole electricity takes 

 place at a lower potential than that which would result if the 

 whole quantity of electricity passing in each single discharge 

 were accumulated upon the electrodes. For then, if the num- 

 ber of discharges were increased ten times, the heat produced 

 would become one tenth as great. The flow of electricity 

 cannot, however, take place completely at tho potential which 

 is necessary for the commencement of the discharge, since 

 then the heating would be independent of the number of dis- 

 charges. We must rather assume that the discharge takes 

 place at an intermediate potential, inasmuch as the electricity 

 cannot flow off through the gas as fast as it flows in through 

 the spark-length, and consequently becomes stored up. 



