Nipher — On the Nature of the Electric Discharge. 5 



a substance having gaseous form. In a gas we may have 

 freely moving positive ions as well as freely moving nega- 

 tive ions. This is the condition in the Geissler and 

 Crookes tubes. In a solid conductor we may also have a 

 displacement of negative ions. The positive ions cannot 

 move. They constitute the conductor. In such a con- 

 ductor, so far as position is concerned, molecules are al- 

 ways and constantly related to neighboring molecules as 

 gaseous molecules are when they collide. The lower the 

 temperature of the solid, the more nearly the molecules 

 approach each other, and the more easily negative ions or 

 particles are displaced from molecule to molecule. In 

 other words, conduction is improved by a decrease of 

 temperature. In the solid conductor, there is no evidence 

 of the existence of a positive current. The positive ions 

 which exist in the gases of the Crookes and Geissler tubes 

 could not flow through a copper wire. 



There has been of late a tendency to return to the one- 

 fluid theory. A few phenomena will be described which 

 appear to favor Franklin's view of the nature of elec- 

 tricity. 



In 1900 in a paper in these transactions entitled, "On 

 Certain Properties of Light-Struck Photographic 

 Plates," 3 1 have described a phenomenon which has some 

 resemblance to what has been called ball lightning. Fig- 

 ures 8, 9 and 10 of that paper show traces on a photo- 

 graphic film, made by a slowly moving point of light. The 

 motion of the point of light was always in the direction 

 of flow of a negative discharge, and came from the nega- 

 tive terminal of an influence machine. A metal disc hav- 

 ing a diameter of a centimeter was armed with a pin- 

 point. The point was bent over so that when the disc was 

 placed on the film, the point made intimate contact with 

 the film. The point rested upon a short pencil mark on 

 the film. A slight moistening of the pencil mark is of ad- 

 vantage. The knobs of the machine should be widely sep- 

 arated, and it is of advantage to place a large sheet of 



3 Trans. Vol. X, No. 6. 



