 In August the group showed that the rate of fission in uranium oxide was increased by immersion in ordinary water.During the same summer, the government of Édouard Daladier was able to purchase 185 kg of heavy water from Norsk Hydro in Norway and secretly fly it to France, for the use of the Collège de France team.With the German occupation of Paris in May 1940, Halban and Kowarski left Paris with the supply of heavy water, a gramme of radium and the documentation of their research, as instructed by Joliot-Curie.