

Titanium, and Vanadiumby Therm-electronic 'Currents. 261 



regions of various hydrocarbon flames. As was already 

 stated at the beginning of this paragraph, the first band to 

 appear under red fringe conditions is 3883. As the intensity 

 of thermo-electrical excitation increases, the various groups 

 of bauds appear in the order as given in the table — namely, 

 first the so-called cyanogen bands and finally those of the 

 Swan spectrum. Now this order of development of the 

 carbon spectrum is reversed when chemical excitation is the 

 cause of their emission. With the feebler chemical actions 

 in the air-coal gas cone the Swan bands appear indeed alone, 

 and it is only in the cone of the oxy-acetylene flame, where 

 chemical actions of a very violent nature prevail, that the 

 bands at 3883 and 4216 are likewise brought out. It is also 

 well to mention the fact that the carbon bands are not 

 emitted by the hottest parts of these flames — namely, the 

 region in the mantle just above the cone ; hence their emis- 

 sion cannot be caused solely by thermal or thermo-chemical 

 actions, and this conclusion agrees well with the results of 

 the present experiments. 



Red bands of unknown origin. 



X. Relative intensity. 



6059 1 



*6176 2 



*6313 2 



*£±$2 1 



As these bands have no well-developed edges the settings 

 were made upon their middles, as nearly as was possible to 

 judge. The numbers representing their wave-lengths have 

 therefore no pretence to accuracy. 



To visual observation these bands constitute the most 

 prominent and characteristic feature of the whole fringe 

 spectrum. It is indeed to them that the peculiar red colour 

 of the fringe owes its origin. In appearance these bands 

 are extremely hazy, no edge or other structure being- 

 discernible ; nor has it so far been possible to identify them 

 with an}* known bands, although one of them — namely 618, 

 falls very near a well-known calcium band. A higher 

 dispersion will no doubt solve their mystery. 



