500 Prof. H. Crew on the 



Table I. 

 Arc-Spectrum of Magnesium in an Atmosphere of Hydrogen. 



Wave-length of lines which are 

 relatively 



Eemarks. 



Intensified. 



Weakened. 



Unaffected. 







5711-31 



5528'64 









5183-79 

 5172-86 

 5167-50 



1 Second Subordinate Series of Kayser 

 and Runge. 





[5007-47] 





First head of magnesium-oxide flut- 

 ing. This, and the six following 

 bands, are completely blotted out 

 owing to the absence of oxygen. 







4730-42 



Line too weak for comparison. 







4703-18 



Widened towards red. 





4571-28 





Intensity halved. 



4481 







Intensity increased, perhaps, ten 

 times : line enormously widened : 

 does not appear in the ordinary 

 carbon-magnesium arc. 







4352-08 



Widened towards red. 





[4216-12] 



[3883-55] 



4167-81 



405 8-45 

 3987-0 8 



Cyanogen, Band II., which ordinarily 

 appears as an impurity, is com- 

 pletely blotted out, owing to the 

 absence of nitrogen. 



Cyanogen, Band III., impurity, com- 

 pletely blotted out. 







3838-44 

 3832-45 

 3829-50 



1 First Subordinate Series of Kayser 

 and Runge. 





[3590-48] 





Cyanogen, Band IV., does not quite 

 disappear from my negatives. 







3336-82 

 3332-33 

 3330-04 



1 Second Subordinate Series. 







3097-01 

 3093-09 

 3091-18 



t First Subordinate Series. 



