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

_In this Second Edition of these Opticks I have omitted the Mathematical
Tracts publish'd at the End of the former Edition, as not belonging to
the Subject. And at the End of the Third Book I have added some
Questions. And to shew that I do not take Gravity for an essential
Property of Bodies, I have added one Question concerning its Cause,
chusing to propose it by way of a Question, because I am not yet
satisfied about it for want of Experiments._

_I. N._

July 16, 1717.

Advertisement to this Fourth Edition

_This new Edition of Sir_ Isaac Newton's Opticks _is carefully printed
from the Third Edition, as it was corrected by the Author's own Hand,
and left before his Death with the Bookseller. Since Sir_ Isaac's
Lectiones Opticae, _which he publickly read in the University of_
Cambridge _in the Years 1669, 1670, and 1671, are lately printed, it has
been thought proper to make at the bottom of the Pages several Citations
from thence, where may be found the Demonstrations, which the Author
omitted in these_ Opticks.

* * * * *

Transcriber's Note: There are several greek letters used in the
descriptions of the illustrations. They are signified by [Greek:
letter]. Square roots are noted by the letters sqrt before the equation.

* * * * *

THE FIRST BOOK OF OPTICKS

_PART I._