400 



XIPHER— DISRUPTIVE DISCHARGES 



[April 21, 



An attempt was made to compare the conduction-properties of a 

 drainage column of air like that shown in Fig. i, with those of the 

 flame of a blast lamp. Fig. 2 shows a camera photograph of dis- 

 ruptive discharges between a red-hot ball of iron hung on a wire 

 suspension by means of which it was grounded, and the negative 

 terminal of the influence machine. The ball was heated by a blast 

 lamp, the air being fed from a tank at about two atmospheres pres- 

 sure. A similar flame was ]')laced between the hot ball and the nega- 



FlG. 



tive terminal, so that the discharges passed through it. On account 

 of the long exposure, the contrast between the flame and the indi- 

 vidual sparks is not very distinct. Some of the sparks show a par- 

 tial photographic reversal. The discharge lines are, however, all 

 more or less clearly visible within the flame. Fig. 3 shows a single 

 spark, made under the same conditions, although the flame was 

 exposed for nearly half a minute before the spark passed. Fig. 4 

 shows a similar photograph in which the exposure to the flame was 

 not over half of a second. There are two discharge lines visible, 



