MORSE. — SPECTRA OP 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 

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

 bearinij 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. 



Arc. Metallic lead on carbon electrodes. 



Wehnelt. Lead wire in hydrochloric acid. 



* Ibid., 12, 167 (1900). 



