[ '24 ] 



would occupy. All the red light therefore is not homogeneous ; 

 but confifts of rays of innumerable, different degrees of refran- 

 gibility ; and fo of the other colours. 



Now fince the rays which are of the fame denomination of co- 

 lour are differently refrangible, they will either form oblong 

 fpedrums detached from each other ; or they will in part lap over, 

 and fall on each other. The former pofition is manifeftly falfe : 

 therefore the original prifmatic colours will partly lap over and 

 fall on each other, and therefore neceffarily generate the interme- 

 diate colours. And fo Sir I. Newton obferves, where he fays, 

 that the original, prifmatic colours will not be difturbed by the 

 intermixture of the conterminous rays, which are intermixed 

 together. This overlapping however, which Newton fpeaks of, 

 arifes only from the fun's having a fenfible diameter, and does 

 not neceffarily imply an equal refrangibility in any differently co- 

 loured rays. If there be but three original prifmatic colours, 

 red, yellow and blue, and that the red and yellow lap over, fo as 

 that there fliall be a certain fpace in the fides of the fpedrum 

 equally occupied by yellow and red circles, then will thefe circles 

 by their intermixture compound an orange colour ; and this co- 

 lour as to refrangibility will be homogeneous, becaufe the coin- 

 cident rays of different colours are equally refrangible. In like 

 manner green may be compounded by the mixture of blue and 

 yellow circles, equally refrangible. Now this is fimple, and con- 

 formable to the other phenomena of the fpcdrum ; for if rays of 



the 



