382 The Electrical Conductivity of the JEther. 



heating the spark in the primary of a Thomson-Tesla trans- 

 former produced any marked change in the high-tension 

 spark of its secondary. It was evident that it was detrimental. 

 The high-tension sparks immediately ceased to jump at the 

 extreme sparking-distance of the terminals. Following this 

 train of thought I next placed a spark-gap of the primary of 

 the above-mentioned transformer between the poles of a very 

 powerful magnet, giving a field of certainly ten thousand 

 lines to the centimetre. It is well known that when such a 

 field is excited, the primary spark appears to be blown out 

 with a loud report and a great increase of length of spark is 

 obtained in the secondary of the transformer. Applying the 

 same method, I photographed the spark of the additional 

 spark-gap and found no difference in resistance whether the 

 magnetic field w T as excited or not : or when the spark jumped 

 across the magnetic lines or in the direction of the latter. Is 

 it possible that the aether being already under a magnetic 

 stress, the addition of a powerful electrostatic stress serves to 

 suddenly break down the aether? It is well known that a 

 blast of air imitates the action of the magnetic field. It 

 probably does so by blowing out the voltaic arc which tends 

 to form. It may be that the electrodynamic repulsion com- 

 pels the spark not to follow, so to speak, the voltaic arc and 

 its current of heated air. The loud report may indicate a 

 sudden stress in the medium, and in the case of the Crookes 

 tube the highly rarefied medium within it, would effectually 

 prevent our hearing a similar report. 



I next placed the primary spark of the Thomson-Tesla 

 transformer near a Crookes tube which was giving out the 

 Eontgen rays. I could not perceive any mutual effect. 

 The effect, moreover, of ultra-violet light on the resistance of 

 sparks in air could not be detected. 



The method I have outlined enables one to form an estimate 

 of the energy incident upon the production of the Eontgen 

 rays. It can also measure with greater accuracy than has 

 been possible hitherto the resistance of sparks in air and 

 different media. It show T s conclusively that the discharge in 

 a Crookes tube at the instant when the Eontgen rays are 

 being emitted most intensely is an oscillatory discharge. In 

 popular language, it can be maintained that a discharge of 

 lightning a mile long, under certain conditions, encounters no 

 more resistance during its oscillations than one of a foot in 

 length. In other words, Ohm's law does not hold for electric 

 sparks in air or gases. Disruptive discharges in gases and in 

 air appear to be of the nature of voltaic arcs. Each oscilla- 

 tion can be considered as forming an arc. It is well known 



