I heartily beg that what I have here done may be read with candor; and that the defects I have been guilty of upon this difficult subject may be not so much reprehended as kindly supplied, and investigated by new endeavors of my readers.
Cambridge, Trinity College, ISAAC NEWTON.
May 8, 1686 [Footnote A: Sir Isaac Newton, the great English mathematician and physicist, was born at Woolsthorpe in 1642, and died at Kensington in 1727.

He held a professorship at Cambridge, represented the University in Parliament, as master of the mint reformed the English coinage, and for twenty five years was president of the Royal Society.

His theory of the law of universal gravitation, the most important of his many discoveries, is expounded in his "Philosophiae Naturalis Principia Mathematical," usually known merely as the "Principia," from which, this Preface is translated.].