French physicist who made many contributions to the study of X rays. (X-ray)

After graduating from the École Navale (Naval School), he served as a naval officer for nine years. He turned to the physical sciences about 1904 and founded his own well-equipped laboratory at the family mansion in Paris, where he and other physicists collaborated in experimentation, especially relating to atomic structure. He improved the accuracy of X-ray spectrography by introducing the rotating crystal method and used X-ray techniques to measure the forces binding various groups of electrons to the atomic nucleus. He was elected to the Académie Française in 1934 and became a foreign member of Britain's Royal Society in 1946. From 1942 to 1946 he was a professor at the Collège de France. On his death without direct heirs, the ducal title passed to his brother, Louis.