io8 Mifcellanea Cur to fa. 



*Tis ever compounded, and to its Compofition 

 are reguifite all the aforefaid primary Colours, 

 mix'd in a due proportion. I have often with 

 admiration beheld, that all the Colours of the 

 Prifm being made to converge, and thereby to 

 be again mixed as they were in the light before it 

 was incident upon the Prifm, reproduced light, 

 intirely and perfectly white, and not at all fenfi- 

 bly differing from a direft light of the Sun, ua- 

 lefs when the Glaffes, I ufed, were not fufficient- 

 ly clear ; for then they would a little incline it 

 to their Colour. 



8. Hence therefore it comes to pafs, that 

 l&hitenefs is the ufual Colour of Light ^ for Light 

 is a confufed aggregate of Rays, indued with all 

 forts of Colours, as they are promifcuoufly darted 

 from the various parts of luminous Bodies. And 

 of ftch a confufed aggregate, as I (aid, is genera - 

 red Whitenefs, if there be a due proportion of the 

 Ingredients; but if any one predominate, the 

 Light muft incline to that Colour ; as it happens 

 in the blue Flame of Brimftonc, the yellow 

 Flame of a Candle, and the variours Colours of 

 the fixed Stars. 



9. Thefe things confider'd, the manner, how 

 Colours are produced by the Prifm, is evident. 

 For, of the Rays, conftituting the incident 

 Light, fince thofe which differ in Colour pro- 

 portionally differ in Refrangibility, they by their 

 unequal Refractions muft be fevered and difper- 

 fed into an oblong Form, in an orderly fuccef- 

 fion, from the leaft refracted Scarlet to the mod 

 refracted Violet. And for the fame reafon it 

 is, that Objects, when look'd upon through a 

 Prifm, appear coloured. For the difform Rays, 

 by their unequal Refractions, are made to diverge 

 towards fever al parts of the Retina, and there ex- 



prefs 



