534 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



of the arc, the long band in the violet, which was not examined by 

 Hasselberg, should be very easy of access. 



SILVER. 



Spark. Silver electrodes. 



Arc. Metallic silver on carbon electrodes. 



Wehnelt. Silver wire in hydrochloric acid. 



With silver as active electrode striking differences of intensity from 

 those obtained in the spark and arc are the rule. Only a few lines come 

 out strongly enough to be reproduced, and the spectrum is in general 

 more like that of the arc than that of the spark. This is shown by the 

 lines at X 4055.5, X 4212.0, X 4476.0, X 4668.0, X 5465.0. A number of 

 lines which are strong in the arc are not visible, as, e. g., X 5471.0, and 

 others are much weaker, like X 3682.0. 



Traces of what appears to be an underlying band spectrum are visible, 

 but the maxima are of such small intensity that a very long exposure 

 would be required to bring out the structure clearly. Such maxima as 



