Dr BREWSTER on a New Analysis of Solar Light. 127 



This remarkable structure of the spectrum will be better un- 

 derstood from Plate B, where Figs. 1, 2, and 3, represent the 

 three separate spectra, which are shewn in their combined state 

 in Fig. 4. 



In all these figures the point M corresponds with the red, or 

 least refrangible extremity of the spectrum, and N with the 

 violet, or most refrangible extremity ; and the ordinates ax, bx, 

 ex, of the different curves MRN, MYN, MBN, represent the 

 intensity of the red, yellow, and blue ray at any point x of the 

 spectrum. 



If the distance M an in all these spectra be equal, then, in the 

 combination of them shewn in Fig. 4., the ordinates ax, bx, ex, 

 will indicate the nature and intensity of the colour at any point 

 x of the red spectrum. Thus, let 



The ordinate for red light ax = 30 

 yellow bx = 16 

 blue ex 2 



ax + bx + cx 48 rays, 



then the point x will be illuminated with 48 rays of light, viz. 

 30 of red, 16 of yellow, and 2 of blue light. 



Now, as there must be certain quantities of red and yellow 

 light, which will form white, when combined with 2 blue rays, 

 let us assume these, and suppose that white light, whose inten- 

 sity is 10, will be formed by 3 red, 5 yellow, and 2 blue rays; 

 hence it follows that the point x is illuminated by 



Red rays, - 27 



Yellow rays, - - 11 

 White light, - - 10 



i ' 

 48 rays, 



R 2 



