MORSE. — SPECTRA OF WEHNELT. 



539 



of the atmosphere of mixed hydrogen and oxygen is suggested, though 

 other cases (see aluminium and magnesium) seem to indicate the pre- 

 ponderence of the action of the oxygen freed by the dissociation of the 

 water vapor. 



Some evidence in the matter is given by the research of Crew * on 

 the arc spectra of metals in hydrogen. The results which seem to have 

 bearing in this case are : — 



" I. All lines in the arc spectrum which are affected by hydrogen, 

 whether enhanced or diminished, belong to the spark spectrum also. 



" II. Lines which belong to Kayser and Runge's series are unaffected 

 by the change from air to hydrogen." 



These conclusions cannot be applied as a whole to the spectra of 

 the Wehnelt, but something very similar to the second of them seems 

 to be true for zinc, tin, and lead. (Vid. lead.) 



LEAD. [Plate 1, Fig. 6.] 



Spark. Lead electrodes. 



Are. Metallic lead on carbon electrodes. 



Wehnelt. Lead wire in hydrochloric acid. 



* Ibid., 12, 167 (1000). 



