﻿362 Mr. F. Lloyd Hopwood on a Qualitative 



0*09] 5 per cent, of radium emanation remained uncondensed 

 in the one determination that was made. 



(8) The condensation of thorium emanation in a highly 

 exhausted tube was also studied. 



(9) When the two emanations are mixed in such a tubo 

 the radium emanation appears to be more easily condensed. 



(10) This may not be due to a real difference in the con- 

 densation points but is probably caused by the rapid disinte- 

 gration of the thorium emanation. 



(11) In one experiment indirect evidence was obtained 

 which seems to point to thorium and radium emanations 

 being non-separable by condensation. 



I desire to take this opportunity of expressing my thanks 

 to Professor F. Soddy, F.R.S., for the strong thorium pre- 

 parations and quantities of radium emanation, for the 

 preparation of the tubes employed, and for the section entitled 

 " Theory of the Experiment " in this paper for which he is- 

 responsible. I am indebted to him also for his interest in 

 the experiments throughout their entire course. 



I have to thank Miss Hitchins, B.Sc, also for the capable 

 assistance which she gave me in carrying out the manipula- 

 tions and lengthy measurements involved. 



Physical Chemistry Department, 



Glasgow University. 

 December, 1914. 



XXXIX. On a Qualitative Method of Investigating Thermionic 

 Emission. By F. Lloyd Hopwood, B.Sc., AM.C.Sc* 



THE present writer discovered some time ago f, that the 

 movement of charged bodies in the neighbourhood of 

 a glowing carbon-filament lamp produced, under certain 

 circumstances, a displacement of the loops of the filament. 



Similar observations were recorded by Eve J at about the 

 same time. The results of a further study of the phenomena 

 and their application as a basis of a qualitative method of 

 investigating the emission of electrified particles from in- 

 candescent bodies, are set forth in the present paper. 



Experiments ivith Carbon Filaments. 



"When an electrified rod, charged with electricity of either 

 sign, is brought near an unlighted ordinary 200-volt carbon- 

 filament lamp, the loops diverge in a similar manner to the 



* Communicated by Prof. A. "W. Porter, F.R.S. 

 t ' Nature/ March 1914. % Ibid. 



