Phil. Mas. S. 6. Yol. 1. PI. III. 



No. 1. — Continuous spectrum below. Same deviated 

 by cyanin prism of 17'. 



Nos. 2, 3. — Same with prism of 22'. No. 2 taken with 

 Aurantia screen to reduce effect of blue ; No. 3 without. 



Nos. 4, 5. — Same with prisms of 35" and 2' 51" re- 

 spectively, showing continuity of curve. 



No. 6. — Several exposures with prism of 28' 30". 



