Sir David Brewster on the Radiant Spectrum. 203 



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 M N is the spectrum of the small circular image 

 S, and A B 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 analyze this compound radiation, let the image of 

 the sun S, fig. 1, be taken from homogeneous red light R, fig. 3, 

 and refracted by the prism ; we shall have its radiation a b at a 

 little distance from the bright portion R, as in fig. 3. In homo- 

 geneous yellow light Y, fig. 4, the radiation a b will be at a 

 greater distance from Y than in the red light. In homogeneous 



Kff.7. £DY' 



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Fig. 8. <g|v' 



Fiff-5. (HIV 



Fist 9. 



violet light V, fig. 5, the radiation a b will be at a greater dis- 

 tance from V than in the yellow light. 



P2 



