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First edition, journal issue in original printed wrappers, of the first observation of nuclear fission, four years before Hahn & Strassmann observed it (for which they won the Nobel Prize). In January 1934, Irène Joliot-Curie and Frédéric Joliot announced the discovery of artificial radioactivity: they had bombarded samples of aluminum with alpha particles and induced radioactivity in them. "Curie and Joliot obtained about one disintegration for every million alpha particles impinging on aluminum. The main reason for this low yield is that the aluminum nucleus repels the alpha particles by electrostatic action and prevents them from coming into contact with the target nucleus. It occurred to Fermi that in the case of neutrons there is no such electric repulsion, and that the yield must approach unity . . . These simple considerations induced Fermi to try to use neutrons as projectiles. This departure opened the way to completely unexpected developments. At first, Fermi tried irradiating all the elements he could get his hands on, in order of increasing atomic number. He had no success with hydrogen, lithium, beryllium, boron, carbon, nitrogen, or oxygen, but he was persistent, and finally fluorine showed radioactivity. A period of intense, rapid work followed for the next three years. Fermi and his collaborators, Amaldi, D'Agostino, Rasetti, and I [Segrè] (later also Pontecorvo), at first discovered about forty new radioactive substances. This had great practical and theoretical importance. It provided a great increase in the material for studies on nuclear systematics, and in due course it gave radioactive tracers for practically all chemical elements, thus helping to revolutionize chemical and biological techniques. In the spring of 1934 we irradiated the heaviest element then known - uranium. We found several radioactive periods and substances . . . Furthermore, we showed by chemical means that none of the radioactivities produced in uranium could be ascribed to elements of atomic number greater than that of lead. We then thought that we had produced transuranic elements . . . In this we were in error . . . what we had observed was something quite different" (Segrè, From X-rays to Quarks, pp. 204-5). Ironically, it was not until 1938, the year in which Fermi was awarded the Nobel Prize, "for his demonstrations of the existence of new radioactive elements produced by neutron irradiation, and for his related discovery of nuclear reactions brought about by slow neutrons," that the work of Hahn and Strassmann made it clear that what Fermi's group had observed was not transuranic elements but nuclear fission: neutron bombardment had split the nucleus of uranium to produce nuclei of elements lighter than lead. At the time, nuclear fission was thought by most physicists to be impossible on theoretical grounds, although it had been put forward as an explanation of Fermi's results by Ida Noddack in 1934. Large 8vo, pp. [clxxxv]-clxxxviii, 885-904, i-iv, 905-924, clxxxix-cxcii. Original printed wrappers (corners a bit bumped).
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