This project proposes the first systematic study of the conceptual and experimental foundations of a key episode in the history of science: the establishment of a European consensus on the proper rules of collision by Huygens, Wallis, and Wren promoted by the Royal Society of London in 1668-1669. By mixing Galilean and Cartesian principles with older elements they created a field of inquiry that became a crucial stepping stone to even more ambitious projects of the later Huygens and Newton.