322 ILLINOIS STATE ACADEMY OF SCIENCE 



little below the critical difference for which the positive 

 corona became visible. As soon as the corona appeared 

 in the form of a uniform la3'er of weak light surronnding- 

 the positive wire, then the deflection of the jet of ether 

 was very marked, as indicated in the following photo- 

 grajohic picture and in the drawings made on the screen 

 directly. The deflection could be varied at will by chang- 

 ing the air current through the ether, or the potential dif- 

 ference across the wdres. The two variables could easily 

 be adjusted so that the originally vertical jet was di- 

 rected at right angles and passed a long distance beyond 

 the negative wire. The largest deflections were obtained 

 w^hen the capillary was set between the two wires about 

 5 mm. away from the positive wire. See Fig. 1. But even 

 when the capillary was placed behind the negative wire 

 or in front of the positive wire, a marked deflection was 

 obtained, as can be seen from Fig. 2. Finally, if the 

 capillary was placed about 2 cm. outside the vertical 

 plane containing the wires, a considerable deflection was 

 observed as indicated by Fig. 3. These 3 figures indicate 

 the strong wind blowing from the positive to the negative 

 wire. 



Instead of ether a jet of ammonium chloride or of 

 water vapor can also be used. The water vapor jet ap- 

 peared darker with the corona discharge than without 

 it, indicating the condensation of water vapor around the 

 ions. In the photographic picture the corona took place 

 between a positive wire of 0.3 mm. diameter and a nega- 

 tive wire of 1.25 mm. diameter. It was observed that 

 when the potential difference was applied in the first in- 

 stant the positive wire was surrounded by diffused 

 streamers of light, which disappeared suddenly, giving 

 rise to the uniform positive layer of light. This observa- 

 tion may help to explain the beginning of the corona. 



