11' 



Some Peculiarities of Electric Sparks Across Short 

 Spark Gaps. 



By R. R. Ramsey. 



Bloudlot. in his work ou N-iays, used a very feeble spark gap. lu 

 our attempts to repeat Bloudlot's work ^Nlr. W. P. Haseman and I found 

 some very interesting phenomena Avhich affected the sparking distance 

 and consequently the intensity of the spark. The fact that we were not 

 able to repeat Bioudlot's experiments has led me to make some further 

 investigation. 



T. J. Bowlker (Phil. Mag., 8, p. 487, 1004), has worked with long 

 spark-gaps, 1 cm. to 10 cm. in length, and has obtained some very curious 

 results. 



The work here described was with a spark gap between platinum 

 ■nares .45 mm. in diameter and never more than J mm. apart. 



The spark-gap was provided with a micrometer so as to make length 

 anything desirable. The gap was connected to the secondary coil of a 

 1-iuch induction coil. The current in the primary coil was cut down by 

 means of resistance until the sparking distance was very small. The 

 gap M'as opened to the point where the sparking just ceased and the 

 effects of various ob.iects were ti'ied. When one's hand or finger was 

 brought within 1 cm. of the gap the sparks appeared. This was attrib- 

 uted to heat. A lighted match had the same effect as did one's breath 

 or a current of hot air. A rod of glass or of brass which had been in 

 the same room caused the effect. Any o1>.iect brought near the gap 

 caused an increase of the number of sparks. 



A No. 20 copper wire 15 em. long caused an increase when brought 

 near the gap or when it was allowed to touch one of the electrodes a 

 short distance from the gap. The effect was more noticeable when the 

 wire was in contact with the negative terminal. Touching the electrode 

 five centimeters from the wire had no effect. The eft"ect was more marked 

 when the wire was at right angles to the gap than when placed parallel 

 to the gap. 



