350 RECORDS. 



C. C. Trowbridge, The Duration of the Afterglow 

 Accompanying the Electrodeless Discharge at Low 

 Pressure. 



The regular annual election of officers of the section was then 

 held, which resulted as follows : 



Chairman — Ernest von Nardroff. 



Secretary — C. C. Trowbridge. 



Summary of Papers. 



Mr. Tufts pointed out that the so-called saturation currents, 

 obtained by Wilson and other investigators of the phenomena 

 of electrical conduction through flame gases, were not true satur- 

 ation currents, but only apparently so, owing to the development 

 at the kathode of a high resistance, when the impressed electro- 

 motive forces were over a few volts. By the use of a kathode 

 coated with calcium oxide and heated by a separate flame, 

 it was shown that the resistance of a flame connecting this 

 with the flame remained practically constant. In other words, 

 the current through the connecting flame increased directly 

 as the potential gradient for gradients ranging from a few tenths 

 of a volt to the centimeter up to gradients of as much as 

 fifty volts to the centimeter. It was stated that experiments 

 had been tried with the ordinary luminous gas flame as well as 

 with flames rendered nonluminous by the admixture of air, and 

 the relation between current and potential gradient w^as found 

 to be the same for both kinds of flames. It was stated that 

 experiments were in progress in which higher gradients than 

 fifty volts to the centimeter were to be used. 



Dr. Trowbridge stated that the purpose of the investigation 

 was to determine the nature of the glow that often appears 

 after the cessation of the electrodeless discharge in gases at low 

 pressures. Measurements made thus far on the duration of the 

 glow in air, show a sharp maximum of duration between . i and 

 .05 millimeter pressures and that this maximum point varies 

 with the electrical conditions of the experiment. It was also 

 determined that there is a critical point between .7 to .3 milli- 

 meter pressures where the glow is only occasionally formed. 



