147 
of Edinburgh, Session 1866-67. 
9. Cryolite. Flame yellow , but green at top. Bright lines in 
the green, and a very remarkable and bright one in the yellow 
close to D. There are lines also in the red , and the yellow light 
is unusually copious. 
10. Muriate of Barytes . Flame green. The lines splendid. 
Two in the blue, two in the green, four in the yellowish green , and 
two in the red . 
3. On tlie Radiant Spectrum. By Sir David Brewster, 
K.H., F.R.S. 
I have given the name of Radiant Spectrum to a phenomenon 
which I discovered in 1814, and which I described to this Society 
in the early part of that year. 
It will be understood from fig. 1, which represents the brilliant 
radiation which surrounds a very small image of the sun, when it 
is formed either by reflection or refraction, or otherwise. 
If we now form a spectrum of this radiant image, either by a 
prism or by diffraction, we shall have the radiant spectrum shown 
in fig 2, where MN is the spectrum of the small circular image S, 
M 
Fig. 1. 
and AB the spectrum of the radiation, the centre of which is 
beyond the violet, and nearly in the place where the intensity of 
the chemical or invisible rays is a maximum. 
In order to analyse this compound radiation, let the image of the 
