Vacua, and on Coronoidal discharges. 465 



a Holtz machine for the induction coil and the alternator. In 

 this case the effect was due, of course, to the oscillations pro- 

 duced by the spark discharge between the poles of the machine. 

 The two vacuum bulbs with the water surrounding them act 

 like two condensers connected in series bj the narrow tube. 

 It seems superfluous to describe the obvious experiments which 

 I had to perform to prove the following relation : 



The intensity of the luminosity increases with the condenser 

 surface of the bulbs, with the frequency of alternations, and 

 with the effective electromotive force of the charging appara- 

 tus. Other things being equal the total amount of light pro- 

 duced will increase with the increase of the conductivity of 

 the vacuum. This relation may have been understood before, 

 hut to my knowledge it was never clearly stated. 



The luminous effects which I succeeded in producing in the 

 manner described were so powerful, that I thought it worth 

 while to construct an electrical lamp on this principle. 1 

 mention this for the purpose of pointing out that this method 

 of producing very powerful vacuum discharges was worked 

 out by me several months before the publication of Nikola 

 Tesla's and Professor J. J. Thomson's magnificent experiments. 

 A considerable number of results which I obtained in my ex- 

 periments are simply repetitions, on a small scale, of the results 

 obtained by these scientists. There is, however, one line along 

 which there seems to be but very few points of contact between 

 their work and mine. This line runs in the direction of inves- 

 tigating the relation between the character of the discharge, 

 the pressure in the vacuum, and the effective e. m. f. which 

 produces the discharge. The following experiments will show 

 some of the characteristic features of this relation. 



1. ON THE CRITICAL POINTS OF THE DISCHARGE. 



A vacuum jar of the form and dimensions as given in fig. 8, 

 was substituted for the small double bulb c d, in fig. 7. The 

 bulbs A and B were totally immersed in large glass beakers 

 containing clear, distilled, acidulated water. The air pressure 

 in the bulbs was a little less than 2 mm . Instead of the small 

 alternator a large alternating current machine fed the primary. 

 On closing the primary circuit the discharge between the bulbs 

 started long before the resistance box R, indicated that the 

 e. m. f. in the secondary coil had reached its maximum. The 

 crimson luminosity was very soft, steady, and distributed in 

 accordance with the distribution of the potential which one 

 would expect in an electrical system of the above description. 



Touching the narrow tube at any point increased the lumin- 

 osity below the point touched ; evidently due to the increase 



