NEWTON AND COMPOSITION OF LIGHT 



first, to examine those circumstances, and so tried 

 what would happen by transmitting light through 

 parts of the glass of divers thickness, or through holes 

 in the window of divers bigness, or by setting the prism 

 without so that the light might pass through it and be 

 refracted before it was transmitted through the hole; 

 but I found none of those circumstances material. 

 The fashion of the colors was in all these cases the 

 same. 



" Then I suspected whether by any unevenness of 

 the glass or other contingent irregularity these colors 

 might be thus dilated. And to try this I took an- 

 other prism like the former, and so placed it that the 

 light, passing through them both, might be refracted 

 contrary ways, and so by the latter returned into 

 that course from which the former diverted it. For, 

 by this means, I thought, the regular effects of the 

 first prism would be destroyed by the second prism, 

 but the irregular ones more augmented by the multi- 

 plicity of refractions. The event was that the light, 

 which by the first prism was diffused into an oblong 

 form, was by the second reduced into an orbicular 

 one with as much regularity as when it did not all 

 pass through them. So that, whatever was the cause 

 of that length, 'twas not any contingent irregularity. 



" I then proceeded to examine more critically what 

 might be effected by the difference of the incidence of 

 rays coming from divers parts of the sun ; and to that 

 end measured the several lines and angles belonging 

 to the image. Its distance from the hole or prism 

 was 22 feet; its utmost length 13} inches; its breadth 

 2f ; the diameter of the hole J of an inch; the angle 



VOL. II. 16 229 



