TOL. VIT.] PHILOSOPHICAL TRANSACTIONS, 735 



2. What is the law according to which each ray is more or less refracted ; 

 whether it he that the same ray is ever refracted according to the same ratio of 

 the sines of incidence and refraction ; and divers rays, according to divers 

 ratios; or that the refraction of each ray is greater or less without any certain 

 rule ? That is, whether each ray have a certain degree of refrangibility accord- 

 ing to which its refraction is performed ; or is refracted without that re- 

 gularity ? 



3. Whether rays which are endued with particular degrees of refrangibility, 

 when they are by any means separated, have particular colours constantly be- 

 longing to them, viz. the least refrangible, scarlet ; the most refrangible, deep 

 violet ; the middle, sea-green ; and others, other colours ? And on the con- 

 trary ? 



4. Whether the colour of any sort of rays apart may be changed by re- 

 fraction ? 



5. Whether colours by coalescing do really change one another to produce a 

 new colour, or produce it by mixing only ? 



6. Whether a due mixture of rays, indued with all variety of colours, pro- 

 duces light perfectly like that of the sun, and which has all the same properties, 

 and exhibits the same phaenomena ? 



7. Whether the component colours of each mixture be really changed; or be 

 only separated, when from that mixture various colours are produced again by 

 refraction ? 



8. Whether there be any other colours, produced by refraction, than such 

 as ought to result from the colours belonging to the diversely refrangible rays, 

 by their being separated or mixed by that refraction ? 



To determine by experiments these, and such like quaeries, which involve the 

 propounded theory, seems the most proper and direct way to conclusion. And 

 therefore I could wish all objections were suspended, taken from hypothesis or 

 any other heads than these two ; of showing the insufficiency of experiments to 

 determine these quaeries, or prove any other parts of my theory, by assigning 

 the flaws and defects in my conclusions drawn from them ; or of producing 

 other experiments which directly contradict me, if any such may seem to occur. 

 For if the experiments which I urge be defective, it cannot be difficult to show 

 the defects ; but if valid, then by proving the theory they must render all ob- 

 jections invalid. 



