138 



Mr. S. Bidwell. On the Recurrent 

 FIG. 2. 



[June 7, 



ray from one spectrum passed through, one of the apertures, while a 

 violet ray from the other spectrum passed through the other. 

 These were reflected from the mirror (which was not rotated), and 

 formed two violet disks side by side upon the screen. By adjusting 

 the widths of the slits and the intensities of the limelights, one of 



