This is the first biography of Sir James Chadwick (1891-1974), best known as the discoverer of the neutron, for which he won the Nobel Prize. Chadwick's central role in the unfolding drama of nuclear physics is reflected in his publications and voluminous correspondence (many selections of which are included here) with other leading figures like Niels Bohr and Lord Rutherford. In the 1920s, Chadwick rose to become the operations director of the Cavendish...