It is generally conceived that atomic philosophy was in abeyance, from the time when the authority of ARISTOTLE displaced it, until the days of DALTON. Those who have looked further into the matter are aware of the atomic leanings of GASSENDI about the middle of the seventeenth century, and those of BOYLE and NEWTON which quickly followed. It is, however, seldom realised that there was a continuous chain of atomic thought from the fifteenth century to the time of DALTON. Our purpose here is to trace this thought as far as BOYLE in the works of some of its more striking exponents, not neglecting some of its opponents. The consideration of BOYLE, of NEWTON and of their successors in the eighteenth century demands separate treatment. The current attitude may be illustrated by a statement made by NERNST that DALTON's Atomic Theory (( arose, by one effort of modern science, like a phoenix from the ashes of the old Greek philosophy. )) (i)