An ornamental headpiece featuring a repeating pattern of stylized floral and leafy scrolls within a rectangular border.

P R E F A C E .

A circular library stamp on the right side of the page, showing a shield-like crest in the center.

I wrote this TreatiseFrench: "Traité"; likely referring to his "Treatise on Light." during my stay in France twelve years ago; and I shared it in the year 1678 with the learned individuals who then composed the Royal Academy of SciencesThe French national scientific institution founded in 1666 by King Louis XIV., to which the King had done me the honor of calling me. Several members of this body who are still living may remember being present when I read it aloud, and better than the others, those among them who applied themselves particularly to the study of Mathematics; of whom I can now cite only the celebrated Gentlemen Cassini, Roemer, and De la Hire Giovanni Domenico Cassini, Ole Rømer, and Philippe de La Hire were all world-renowned astronomers and mathematicians of the 17th century.. And although I have since corrected and changed several parts of it, the copies I had made at that time could serve as proof that I have nonetheless added nothing to it, except for some conjectures concerning the formation of Iceland Crystal original: "Cristal d’Islande"; now known as Iceland spar or calcite, famous for its double refraction. and a new observation on the refraction of Rock Crystal original: "Cristal de Roche"; clear quartz.. I wanted to recount these details to make known for how long I have meditated upon these things