Later, the quantity of radium extracted for the laboratory was increased, and in 1907 I was able to make a second and more precise determination of the atomic weight as 225.35--one accepts now the number 226. I succeeded, too, jointly with André Debierne, in obtaining radium in the state of metal. The total quantity of radium I prepared and gave to the laboratory, in agreement with Pierre Curie's desire, amounted to more than a gramme of radium element. The activity of pure radium exceeded all our expectations. For equal weights this substance emits a radiation more than a million times more intense than uranium. To offset this, the quantity of radium contained in uranium minerals is scarcely more than three decigrammes of radium to the ton of uranium. There is a very close relation between these two substances. In fact, we know to-day that radium is produced in the minerals at the expense of uranium. The years that followed his nomination to the P.C.N. were hard for Pierre Curie. He had to face the many anxieties incident to the organization of a complicated system of work when his happiness depended on his being able to concentrate his efforts on a single determined subject. The physical fatigue due to the numerous courses he was obliged to give was so great that he suffered from attacks of acute pain, which in his overtaxed condition became more and more frequent. It was therefore vitally important, if he was to spare his energy and keep his health, that the burden of his professional duties be lightened. He decided to apply for the Chair of Mineralogy, which was vacant, at the Sorbonne, for which he was entirely qualified because of his profound knowledge and his important publications on the theories of the physics of crystals. Yet his candidacy failed. During this painful period he nevertheless managed, by a truly superhuman effort, successfully to complete and publish several investigations that he had made either alone or in collaboration: Investigations on induced radioactivity (in collaboration with A. Debierne). Investigations on the same subject (in collaboration with J. Danne). Investigations on the conductibility provoked in dielectric liquids by the rays of radium and the Roentgen rays. Investigations on the law of the decrease of the emanation of radium and on the radioactive constants that characterize this emanation and its active deposit. Discovery of the liberation of heat produced by radium (in collaboration with A. Laborde). Investigations on the diffusion of the emanation of radium in the air (in collaboration with J. Danne). Investigation on the radioactivity of gases from thermal springs (in collaboration with A. Laborde). Investigation on the physiological effects of radium rays (in common with Henri Becquerel). Investigation on the physiological action of the radium emanation (in common with Bouchard and Balthazard).