74 



THE ROYAL SOCIETY OF CANADA 

 Lead. 



The lead vacuum arc spectrum was obtained by putting lead in 

 iron terminals in the vacuum arc lamp. The arc was alm.ost con- 

 tinuous and very intense, being sustained by a current of 4 amperes. 

 As it was not possible to obtain chemically pure lead, a sample of 

 ordinary lead was used. Hence some of the lines recorded here may be 

 due to impurities. 



