117 



Some Peculiarities of Electric Sparks Across Short 

 Spark Gaps. 



By R. R. Ramsey. 



Bloudlot, in his work on X-rays, used a very feeble spark gap. In 

 onr attempts to repeat Bloudlot's work Mr. W. P. Haseman and I found 

 some very interesting phenomena which affected the sparking distance 

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

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

 investigation. 



T. J. Bowlker (Phil. Mag., S, p. 487. 1904), 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 

 wires .45 mm. in diameter and never more than I 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-inch induction coil. The current in the primary coil was cut down by 

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

 gap was opened to the point where the sparking just ceased and the 

 effects of various objects were tried. 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 object brought near the gap 

 caused an increase of the number of sparks. 



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

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

 short distance from the gap. The effect Avas more noticeable Avhen the 

 Avire Avas in contact with the negatiA'e terminal. Touching the electrode 

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

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

 to the gap. 



