Produced by Suzanne Lybarger, steve harris, Josephine Paolucci and the Online Distributed Proofreading Team at http://www.pgdp.net. OPTICKS: OR, A TREATISE OF THE _Reflections_, _Refractions_, _Inflections_ and _Colours_ OF LIGHT. _The_ FOURTH EDITION, _corrected_. By Sir _ISAAC NEWTON_, Knt. LONDON: Printed for WILLIAM INNYS at the West-End of St. _Paul's_. MDCCXXX. TITLE PAGE OF THE 1730 EDITION SIR ISAAC NEWTON'S ADVERTISEMENTS Advertisement I _Part of the ensuing Discourse about Light was written at the Desire of some Gentlemen of the_ Royal-Society, _in the Year 1675, and then sent to their Secretary, and read at their Meetings, and the rest was added about twelve Years after to complete the Theory; except the third Book, and the last Proposition of the Second, which were since put together out of scatter'd Papers. To avoid being engaged in Disputes about these Matters, I have hitherto delayed the printing, and should still have delayed it, had not the Importunity of Friends prevailed upon me. If any other Papers writ on this Subject are got out of my Hands they are imperfect, and were perhaps written before I had tried all the Experiments here set down, and fully satisfied my self about the Laws of Refractions and Composition of Colours. I have here publish'd what I think proper to come abroad, wishing that it may not be translated into another Language without my Consent._ _The Crowns of Colours, which sometimes appear about the Sun and Moon, I have endeavoured to give an Account of; but for want of sufficient Observations leave that Matter to be farther examined. The Subject of the Third Book I have also left imperfect, not having tried all the Experiments which I intended when I was about these Matters, nor repeated some of those which I did try, until I had satisfied my self about all their Circumstances. To communicate what I have tried, and leave the rest to others for farther Enquiry, is all my Design in publishing these Papers._ _In a Letter written to Mr._ Leibnitz _in the year 1679, and published by Dr._ Wallis, _I mention'd a Method by which I had found some general Theorems about squaring Curvilinear Figures, or comparing them with the Conic Sections, or other the simplest Figures with which they may be compared. And some Years ago I lent out a Manuscript containing such Theorems, and having since met with some Things copied out of it, I have on this Occasion made it publick, prefixing to it an_ Introduction, _and subjoining a_ Scholium _concerning that Method. And I have joined with it another small Tract concerning the Curvilinear Figures of the Second Kind, which was also written many Years ago, and made known to some Friends, who have solicited the making it publick._ _I. N._ April 1, 1704. Advertisement II