314 Prof. L. T. More and Mr. E. Gr. Rieman on 



and magnetic field were varied between wide ranges, from 

 the limit where a simple glow discharge, without negative 

 dark spaces, passed between the anode and cathode, to so 

 great a vacuum that the induction-coil could not produce a 

 luminous discharge at all. The appearance in each of the 

 gases most nearly approaching that in air was a more or less 

 diffuse cathode glow filling about half the large part of the 

 tube with a core of magnetic rays short and sharply conical in 

 shape, lying along its axis. The induced column at the end 

 of these rays with a virtual anode and a reversed curvature 

 was never obtained. If any of these gases were mixed with 

 air, either by admitting a little air into the tube or by not 

 removing all of it, then all the phenomena characteristic of 

 the discharge in air were readily obtained. This fact made 

 it certain that the gases were pure when the phenomena 

 were not obtained. 



Trials were then made with mixtures of the gases. 

 Neither hydrogen or oxygen mixed with carbon dioxide in 

 any proportion gave the effect. The magnetic rays were 

 somewhat longer and larger, and there appeared occasionally 

 a small induced column, but it always bent, in an auxiliary 

 magnetic field, in the same direction throughout all its length, 

 and the curvature indicated a positive current from the end 

 of the magnetic ray column to the far end of the tube. 

 There was no virtual anode in it with the positive current 

 discharging in both directions as shown in fig. 2. 



Mixture of nitrogen and carbon dioxide. — This mixture 

 gave all the effects of air ; both the magnetic rays and the 

 induced column with a virtual anode were observed at the 

 same pressures as for air. The discharge was rather less 

 intense, but the magnetic field was able to condense all the 

 diffuse glow into an axial column. 



Mixture of nitrogen and oxygen. — The appearance was 

 exactly that of air. 



Mixture of nitrogen and hydrogen. — This mixture acted 

 like air but much less certainly. The best proportion of 

 gases was about six parts of nitrogen to one of hydrogen, 

 If the proportionate part of nitrogen was much less, the 

 induced column could not be produced. 



We have been able to repeat satisfactorily the most im- 

 portant phenomena discovered by Professor Righi wdien a 

 magnetic field acts on the cathode rays in a tube containing 

 air ; and we have, in addition, found that the nature of the 

 gas has an important influence on this action. While it is 

 not possible to state fully and exactly what these differences 

 are and what their cause may be, yet our observations point 



