and some of its Compounds. 317 



compound, nor that of the elementary gas, but a carbon spec- 

 trum. This, however, does not mean that we get the line 

 spectrum of elementary carbon ; for it is certain that there is 

 water vapor present in the tubes, notwithstanding the temper- 

 ature to which it has been, subjected. The carbon may then 

 unite with the oxygen of the water vapor, forming either 

 carbon monoxide or dioxide ; the hydrogen being occluded by 

 the terminals or the glass walls. 



Just as the spectra of gaseous carbon compounds in wide 

 tubes with metallic terminals appear identical with the spectra 

 of elementary gases in tubes with carbon electrodes submitted 

 to condenser discharges, so we should expect that the spectra 

 produced would be the same in the two cases This is found 

 to be true. The general appearance of the photographs 

 obtained with continuous currents is very different from those 

 obtained with condenser discharges. In the former case there 

 is a marked band appearance in addition to a line spectrum. 

 The most prominent of these bands in the region studied is 

 the one beginning at 3884. With the dispersion used this 

 band consists of five prominent lines crowding together toward 

 the ultra-violet. A somewhat similar band, apparently of six 

 lines, begins at 4216. Another band, rather faint, consisting of 

 a large number of fine lines shading off toward the ultra-violet, 

 begins at 4126. The bands beginning at 4216 and 4884 

 appear to be the same as the bands which Kayser and Runge* 

 designate respectively as the second and third cyanogen bands 

 in the arc spectrum of carbon in air. 



Besides these bands a number of single lines appear which 

 are common to all the gases. Among these, the most promi- 

 nent are: 



3652 



4048 



4080 



4360 



In the tube filled with cyanogen many of the same lines that 

 appear in tubes with metallic terminals filled with nitrogen 

 are present besides the above. This is true to a certain extent 

 of the other gases ; and it is not surprising, since it is to be 

 expected that some atmospheric air is always present as an 

 impurity. 



The conclusions to be drawn from these experiments with 



steady currents are similar to those we have deduced from 



condenser discharges. When elementary gases are introduced 



into tubes with carbon terminals and exhausted to a pressure 



* Abhandlungen der Akademie der Wissensch. zu Berlin, 1889. 



