Building upon his pioneering investigation of the colours of thin films, Isaac Newton developed two influential theories, one on the structure of matter, explaining the colours of bodies and the other on fits, describing the periodicity of light. Professor Alan Shapiro, editor of The Optical Papers of Isaac Newton, recounts the development of these theories based on his study of Newton's unpublished manuscripts and analyses their experimental foundation. He also shows the essential role that Newton's philosophy of science played in the formulation and reception of these theories. The second part of the book describes a vigourous dispute over Newton's theory of coloured bodies waged by physicists and chemists for nearly fifty years, from the late eighteenth century to the early nineteenth century. Professor Shapiro's analysis of this previously unknown dispute and of the reasons for the chemist's attack on Newton's theory illuminates the nature and relation of physics and chemistry during this seminal period of their development.