A few historical notes

Shortly after the X-ray discovery, H. Becquerel discovered the ''uranic rays'' emitted by the element uranium. M. Curie observed that the minerals including uranium were more radioactive than the uranium they contained; she inferred the presence, as traces, of yet unknown radioactive elements. A few months later, P. and M. Curie discovered polonium and radium. The radium ray ''physiologic action'' was observed for the first time in 1900. E. Rutherford and F. Soddy showed in 1902 that radioactivity was the spontaneous transmutation of one chemical element in another. The atomic nucleus and nuclear reaction discovery, led F. and I. Joliot-Curie to discover, in 1934, artificial radioactivity. 5 refs., 4 photos