P R E F A C E .

regard it, and in the new explanation of its notable propertyHuygens is referring to the laws of refraction and the way light waves spread, which he uses to explain how lenses and vision work., which forms the main foundation of the structure of our eyes, and of those great inventions that so greatly extend their use. I also hope that there will be some who, by following these beginnings, will penetrate further into this entire subject than I have been able to do, since it is far from being exhausted. This is evident from the places I have marked, where I leave difficulties without resolving them; and even more so by the things I have not touched upon at all, such as Luminous BodiesOriginal: "Corps Luiſants." These are objects that produce their own light, like the sun or a flame, as opposed to objects that only reflect it. of various kinds, and everything regarding Colors; in which no one until now can boast of having succeeded. Finally, there remains much more to seek concerning the nature of Light than I claim to have discovered, and I shall owe much in return to whoever can supply what I lack here in knowledge.