413. Since the great asra in science, created by the 
genius of Newton, who first decomposed the solar 
beam, and thus 
" Untwisted all the shining robe of day," 
it has been considered, that " colours are not qua- 
lifications of light, derived from refractions or re- 
flexions of natural bodies (as was generally believed), 
but original and connate properties, which, in divers 
rays, exhibit divers colours*." By means of the prism, 
Sir Isaac Newton was enabled to separate the solar 
beam into seven differently coloured rays, which run 
gradually into each other according to their particu- 
lar degrees of refrangibility. Of these rays, the vio- 
let is the most refrangible ; next the indigo ; then 
follow the blue, the green, the yellow, the orange, 
and the red, which is the least refrangible of all. In 
the property of reflexibility, these rays, also, follow 
the order of their refrangibility. 
414. These primary rays of light are simple and 
homogeneal, and cannot be changed in colour either 
by reflexion or refraction. Different mixtures of 
them may, however, be made to compound colours, 
like to those of homogeneal light ; and various other 
colours, unlike to any of those of the primary rays, 
may be also formed by composition. But the red, 
yellow and blue rays are incapable of being produced, 
like all the rest, by the combination of other colours ; 
they are therefore always simple and uncompounded. 
When all the primary rays are mixed together in due 
proportion, they then constitute white light. 
"* Onpra (~)m tnm. in. n. 
