each of theſe elementary Rays has inherently in it ſelf that which forms its Colour to the Eye, take a ſmall Piece of yellow Wood for Inſtance, and ſet it in the Ray of a red Colour, this Wood will inſtantly be ting'd red; but ſet it in the Ray of a green Colour, it aſſumes a green Colour, and ſo of all the reſt.
From what Cauſe therefore do Colours ariſe in Nature? 'Tis nothing but the Diſpoſition of Bodies to reflect the Rays of a certain Order, and to abſorb all the reſt.
What then is this ſecret Diſpoſition? Sir Iſaac Newton demonſtrates, that 'tis nothing more than the Denſity of the ſmall conſtituent Particles of which a Body is compos'd. And how is this Reflexion perform'd? 'Twas ſuppos'd to ariſe from the Rebounding of the Rays, in the ſame Manner as a Ball on the Surface of a ſolid Body; but this is a Miſtake, for Sir Iſaac taught the aſtoniſh'd Philoſophers, that Bodies are opake for no other Reaſon, but becauſe their Pores are large; that Light reflects
