SECTION III, 1912. [93] Trans. R.S. C. 
On the Resolution of the Spectral Lines of Mercury by Lummer Plates. 
By Proressor J. C. MCLENNAN. 
(Read May 16, 1912). 
In presenting this paper the author showed a number of prints 
which exhibited the resolution of the mercury green line A = 5461 A U 
obtained with (1) an echelon grating, (2) several glass Lummer plates, 
and (3) a Lummer plate made of crystal quartz. The resolution 
obtained with these different types of instruments was practically the 
same and showed the structure of the green line mentioned above to 
consist of a wide main line (probably a doublet) together with three 
satellites of shorter wave length of varying intensities, and two (or 
perhaps three) satellites of different intensities of longer wave lengths. 
