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THE ROYAL SOCIETY OF CANADA 



Aluminium. 



The vacuum arc spectrum for aluminium was obtained by using 

 aluminium alone as terminals in the arc lamp. The arc remained steady 

 for short periods but was mostly intermittent. For the intermittent 

 arc the current was about eight amperes when the terminals touched 

 together, but when separated the current quickly dropped to zero, 

 and therefore it was necessary to separate and touch the terminals 

 continually in order to obtain a photograph. 



