Charles Glover Barkla (1877–1944) was one of the early pioneers in x-ray research. His most important contributions were those showing that x rays could be polarized; that when x-rays were scattered by light atoms the number of electrons in the atoms was about half their atomic weight, and that when x rays were incident on heavy atoms these atoms emitted characteristic or fluorescent radiations, which he called theKandLseries. He explained the latter in terms of the Rutherford-Bohr atom. For the discovery of the characteristic radiations, he was awarded the Nobel prize in 1917. Shortly before this time, he considered that he had discovered a new type of characteristic radiation which he calledJradiation, later modifying the description toJtransformation. Though a great deal of work was done on thisJradiation, he was not really able to substantiate its existence. He essentially never modified his early ideas or apparatus, although important discoveries were being made in x rays by Bragg, Compton, Auger, and others.