454 



CAROLINE W. BALDWIN. 



[Vol. III. 



Copper. 



Copper gives an arc which has a bluish-green center with 

 bright green near the carbons. This is surrounded by a dark 

 part, which is again enclosed by a yellow outer sheath. 



The spectrum appears almost like that obtained from the center 

 of the original arc, with the addition of the lines due to copper. 

 The variation in brightness of certain lines at the positive and 

 negative carbons is very noticeable, and is more easily observed 

 owing to the fact that the copper lines are all strongest about 

 half-way bctzveen the carbons, at which point they show a decided 

 enlargement. In the band spectrum only the fine, grating-like 

 lines are seen. The indications of the strong lines are seen at the 

 negative carbon, while the lines of the band spectrum are strong 

 for the whole width of the arc. 



Copper lines photographed. 



Sih 



'er. 



The appearance of silver in the arc, and its effect upon the 

 spectrum, are almost identical with that of copper. 



Silver lines photographed. 



