WOOD AND FBA>CK. 



Phil. Mag. Ser. 6, Vol. 21. PL II. 



i Resonance Sp. 

 ■< Iodine in vacuo. 

 (. Excitation by 546. 



Barium Arc. Comp. 



( Res. Sp. Iodine in 

 b < vacuo. Excit. 546. 



L Long 



g exposure. 



C Res. Sp. Iodine in 

 c < Helium at 2 mm. 

 (.Excitation by 546. 



C C Fluokesc. Sp. of 

 \d< Iodine in vacuo. 

 (_ (. Excit. by white light. 



Hg. 546 Line. 



Fig. 1, 



