Sir Ernest Rutherford (1871 1937) was a New Zealand-born physicist who has become known as the 'father of nuclear physics' for his discovery of the so-called planetary structure of atoms. He was awarded the Nobel Prize in Chemistry in 1908. His co-authors, James Chadwick and Charles D. Ellis also made significant discoveries in the field of nuclear physics, with Chadwick discovering the neutron particle in 1932. Research in nuclear physics in the 1930s had become focused on investigating the natures of alpha, beta and gamma radiation and their effects on matter and atomic structure. This volume provides a definitive account of the state of research into these types of radiation in 1930, explaining the theory and process behind inferring the structure of the atom and the structure of the nucleus. The text of this volume is taken from a 1951 reissue of the 1930 edition.