Titanium, and Vanadium hy Thermelectronic Currents. 269 

 field was always less than 8 Y —^), the lines of other elements 



become likewise affected under similar temperature con- 

 ditions. It will, further, be shown that the carbon bands 

 originate always at an anode, whereas metal lines are almost 

 invariably associated with a cathode. These various facts seem 

 to me to point to some electrolytic process as underlying the 

 cause of their emission, such as Professor Schuster has sug- 

 gested in explanation of the discharge of electricity through 

 gases. On this view the function of the thermelectronic 

 current would be to decompose molecules of carbon and of its 

 compounds at the surface of the incandescent plate, as well as 

 along the entire path marked by the red fringe and to cause 

 the formation of positive and negative radiating atom-ions. 



§11. Discussion of results and their application to the case 

 of the electric tube resistance furnace. 



The experiments described in this paper have shown most 

 conclusively that, when a plate of graphite is raised to a high 

 temperature by passing an electric current through it, the 

 light radiations given out by the luminous vapours in its 

 vicinity are due to two entirely different emissions, one of 

 which is controlled by the plate temperature and the other 

 one by the thermelectronic current. As was pointed out 

 in § 1, such a plate may be regarded as having been formed 

 by cutting a tube open longitudinally and rolling it out flat. 

 If, now, in like manner we imagine our plate to be rolled 

 back, and its sides to meet and close up again, so as to form 

 a tube once more, would it be justifiable to conclude a priori 

 that the luminous phenomena exhibited by the interior of 

 such a tube, raised to a high temperature by passing an 

 electric current through it, will be fundamentally different 

 in character from those previously observed with the 

 plate ? 



Furthermore, would it be possible to presume without 

 prejudice that all the electric actions, so manifestly promi- 

 nent in the vicinity of a simple plate, will, in the case of a 

 tube-furnace, be quite ineffective and that all the spectro- 

 scopic phenomena observed in such a furnace will be solely 

 controlled by temperature ? 



In order to answer these questions we must examine 

 whether and in how far, the conditions which govern the 

 formation of the thermelectronic current, as revealed by 

 the experiments with a graphite plate, are fulfilled in the 



