294 Mr. G-. A; Hemsalech and the Comte de G-ramont 



camel's hair brush a drop of some transparent liquid, such as 

 distilled water, paraffin oil, glycerine, turpentine, alcohol, 

 etc., is placed in the small gap between them, where it is 

 held in position by capillary forces (fig. 2 a). The electrodes 

 are now brought into contact, and then separated again 

 by swiftly raising the upper electrode to a distance of 

 several centimetres from the stationary one so as to avoid the 

 establishment of a stable arc (fig. 2 b). We estimate that 

 in our experiments the velocity of the electrode as it moves 

 upwards is at least one metre per second, so that the luminous 



Fi* 2. 



Movable 

 poles 



V^y Path of 

 arc flash 



a. b. 



Method of producing arc in liquid media. 



phenomena 'observed along the path of the arc follow each 

 other in rapid succession. The relative position of any 

 luminous effect along the gap will therefore provide us with 

 an indication as to which part of the discharge it corresponds. 

 The luminous phenomenon obtained in the way described 

 is composed of two distinct phases. At the instant the 

 electrodes separate a discharge begins to pass between them 

 through the thin liquid film. When the distance between 

 the electrodes has grown to from about 0"1 to 0'5 millimetre, 

 varying according to the nature of the liquid, the first phase 

 of the phenomenon comes to an end with the destruction of 



