In the final years of the nineteenth century, the experiments of Rontgen with x-rays; of Henri Becquerel with mysterious emanations which exposed photographic plates, and of the Curies with "new" radium, made it clear that previous understanding of the chemical elements was totally inadequate. There was, these scientists found, a whole new world of elements which by natural alchemy were being transmuted into a new array of isotopes, emitting a variety of "rays" in the process. In the twenty years before WWI the greatest intellects of many countries, devising hundreds of brilliant experiments, mapped this unknown territory of the atom. The Restless Atom is the first history of the scientific progress of those years - and of the scientists, particularly Ernest Rutherford, who discovered the radioactivity of nature and saw in the radioactive transmutation of atoms the patterns on which the science of the atomic age is now being built.