Titanium, and Vanadium by Thermelectronic Currents. 251 



the velocity of the upmshing air will not vary appreciably, 

 we may expect that some stable regime will become estab- 

 lished in which there are no rapid variations in the position 



Fig-. 3. 



MM # 



Rising vapours 



Carborundum 

 powder 



Graphite 

 plate 



B!u/sn vapours 



Plate temperature : 2300-2700° C. 



of the boundary surface between the vapours and the sur- 

 rounding air currents. The sharply defined outline of the 

 bluish vapour might accordingly be caused by a steady 

 state of the acting forces and by the continual clearing 

 away of the superfluous vapours through the upward rush 

 of air. 



Although the existence of appreciable ionization currents 

 through the luminous vapours, under these temperature con- 

 ditions, was easily shown by means of a pair of exploring 

 electrodes, the spectroscopic results did not, however, indi- 

 cate that the light radiations emitted by these vapours were 

 entirely governed by them. A most remarkable effect, both 

 luminous and spectroscopic, was however observed when 

 the graphite plate was raised to a temperature of about 

 3000° C. In immediate contact with the undersurface of 

 the hot plate and suspended from it as it were, there ap- 

 peared a sharply defined luminous band of pinkish hue, 

 stretching right across the space between the clamping bars 



