Of the properties of BODIES, upon which their COLOURS depend.
AFTER having shewn in the last chapter, that the difference between the colours of bodies viewed in open day-light is only this, that some bodies are disposed to reflect rays of one colour in the greatest plenty, and other bodies rays of some other colour; order now requires us to examine more particularly into the property of bodies, which gives them this difference. But this our author shews to be nothing more, than the different magnitude of the particles, which compose each body: this I question not will appear no small paradox. And indeed this whole chapter will contain scarce any assertions, but what will be almost incredible, though the arguments for them are so strong and convincing, that they force our assent. In the former chapter have been explained properties of light, not in the least thought of before our author’s discovery of them; yet are they not difficult to admit, as soon as experiments are known to give proof of their reality; but some of the propositions to be stated here will, I fear, be accounted almost past belief; notwithstanding that the arguments, by which they are established are unanswerable. For it is proved by our author, that bodies are rendered transparent by the minuteness of their pores, and become opake by having them large; and more, that the most transparent body by being reduced to a great thinness will become less pervious to the light.
2. BUT whereas it had been the received opinion, and yet remains so among all who have not studied this philosophy, that light is reflected from bodies by its impinging against their solid parts, rebounding from them, as a tennis ball or other elastic substance would do, when struck against any hard and resisting surface; it will be proper to begin with declaring our author’s sentiment concerning this, who shews by many arguments that reflection cannot be caused by any such means[295]: some few of his proofs I shall set down, referring the reader to our author himself for the rest.