CHAD I consists of papers and letters relating mainly to Chadwick's atomic energy work. The material in CHAD II is correspondence relating largely to Gonville and Caius, a little scientific correspondence and some mainly ephemeral items with a few articles and offprints. CHAD III contains the scientific notebooks of Sir James Chadwick and Professor Sir Ernest Rutherford as well as correspondence with individuals and about non-Atomic Energy work. CHAD IV contains Chadwick's Atomic Energy papers including correspondence and notebooks.