Newton's observations of diffracted rays

The history of diffracted rays is usually considered to be less than a century long. However, a careful study of experiments and observations made by Newton and described in his Optiks shows that diffracted rays had been observed nearly 300 years ago. To show this is the goal of the present paper. Optiks Book III, part I, also comprehends diffraction. Of the various observations by Newton in that book, two have been chosen in the present paper to demonstrate, by applying modern theories, that Newton was actually observing diffracted rays.