144 



Observations on the Electric Arc. 



Fig. 14 shows the variation of amperes and watts for 

 both fall and time. In the carve of amperes against time 

 there appears to be a lower limit of about 4 amperes under 

 which the arc of 0*05 in. length will not restart. This 

 accords with experiment. 



A copper-carbon (solid) arc in air would not restart with 

 an interruption of 0*072 sec, when the readings for the 

 arc were 22 volts, 12'2 amperes, and 0*03 in. arc-length. 



A copper-carbon (cored with K 2 S0 4 ) arc in air restarted 

 as follows : — ■ 



Volts. 



Amperes. 



Arc Length 

 (inches). 



Fall 



(feet). 



Time 

 (seconds). 



125 

 12-5 



13 

 125 



005 

 003 



0-083 

 0125 



0072 



0-088 



A carbon (cored with K 2 S0 4 ) -copper arc in air would not 

 restart with an interruption of 0*072 sec, when the readings 

 were 17 volts, 13 amperes, and 0*05 in. length. 



A copper-carbon (solid) arc in air could not he made to 

 restart with the smallest obtainable interruption, 0*051 sec, 

 when its readings were 19 voJts, 12*5 amperes, and 0*02 in. 

 length. It did restart, however, when the arc-length was 

 reduced to about 0*01 in. 



A copper-carbon (solid) arc in coal-gas could not be made 

 to restart at 23 volts, 14 amperes, and 0*01 in. length, in the 

 shortest obtainable time of interruption. Even after running- 

 it some time, to obtain a good deposit of carbon on the copper, 

 it would not restart. 



A copper-carbon arc in hydrogen could not be made to 

 restart at all. Its 



readings w^ere as follows 



Volts. 



Amperes. 



Arc Length 

 (inches). 



Time of Interruption 

 (seconds). 



32 



12 



002 



0-056 



24 



13 



01 



0-051 



23 



14 



0005 (approx.) 



0-04 



In conclusion, the author wishes to express his indebted- 

 ness to Dr. J. A. Fleming, F.R.S., and to Mr. W. C. Clinton, 

 B.Sc, for their kind assistance during the progress of this 

 work. 



