ELECTRON EMISSION FROM GLOWING SOLIDS. 
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and II. are for the Nernst filament when heated in the usual manner by conducting 
an alternating current. Two curves are given so as to show the magnitude of the 
variation of the negative emission with this method of heating. The curves represent 
the last two series of observations made before the filament was broken up. Curve II. 
was obtained immediately after heating at a high temperature in air at atmospheric 
pressure, and Curve I. shows the values to which the emission had risen after heating 
for some hours in a vacuum. The increase is rather greater than that obtained when 
the material on the platinum tube was similarly treated. The corrected “ steady 
values ” of the emission from the material of this filament when heated on the platinum 
tube are shown in Curve III. The differences between these values and those given 
by the filament itself are not greater than the differences often obtained in observations 
Curves I. and II. are for a Nernst filament heated by an alternating current. 
Curve III. is for the material of a Nernst filament heated upon platinum. 
of the thermionic current from a glowing cathode under apparently identical conditions 
at different times, and we may safely conclude that there is no marked difference 
between the emission from the material heated upon platinum—when practically none 
of the heating current flows through it—and that obtained when the material is 
heated by conducting an electric current. Such a result could not be obtained if the 
electrons are liberated only as a result of the chemical action between the products of 
electrolysis of the material of the filament. 
It has been mentioned that the emission from the material heated upon platinum 
was, at first, considerably less than that from the platinum alone, and that this emission 
gradually increased up to a steady value in the course of three or four hours’ heating. 
VOL. ccxiv.— a. 2 P 
