2 Trans. Acad. Sci. of St. Louis. 



Figs. A and B, Plate I, of this paper, have been pro- 

 duced in the same manner as Figs. B and C of the former 

 paper, excepting that the copper plate was not removed. 

 There was a small hole through the copper plate, which 

 permitted a small section of the positive column to pass 

 through, but this did not affect the form of that part of 

 the column which was cut off. 



It appears from recent work that the form of the dis- 

 charge streamers across the main gap to the copper 

 plate or to the negative terminal, if the plate is removed, 

 is determined mainly by the width of the two gaps a and 

 a', in the approach lines. In these gaps there is a con- 

 tinuous surging to and fro of air molecules. It is evi- 

 dently a time alternation of convection and conduction 

 discharge. In the one case the negative corpuscles are 

 carried across the gap by super-charged molecules. This 

 is a dark discharge. When these molecules return they 

 have lost not only the excess but a part of their own 

 normal charges. They then form a conductor, through 

 which a luminous transfer by conduction takes place. 

 These vibrations show their presence by musical tones 

 of high pitch. The pitch of these notes rises as the gaps 

 a and a are made shorter. The sounds cease when these 

 gaps are closed. In Fig. A of Plate I, a minute gap of 

 less than a mm. existed in the negative approach line at 

 a. In B this gap was closed and a similar gap was made 

 at « in the positive line. In Fig. C, both gaps were 

 closed. In each case a flash light was used at the end of 

 a five-minute exposure, in order to secure an image of the 

 knobs. The diameter of the knobs was 1.8 cm. 



AVhen both gaps a and a are closed and the lines lead- 

 ing from the machine terminals to the main gap are 

 metallic throughout, as in Fig. C of Plate I, an active 

 negative glow exists in front of the negative knob. The 

 mica windmill, described in the last paper, shows that the 

 air is being urged across the dark space to the copper 

 plate. In the gap between the copper-plate and the posi- 

 tive knob, there were no luminous streamers, but they 



