Following British physicist Charles Glover Barkla 's discovery of characteristic X-rays emitted from metals in 1906, British physicist Henry Moseley considered a possible correlation between X-ray emissions and physical properties of elements. Moseley, along with Charles Galton Darwin, Niels Bohr, and George de Hevesy, proposed that the nuclear charge (Z) might be mathematically related to physical properties. The significance of these atomic properties was determined in the Geiger–Marsden experiments, in which the atomic nucleus and its charge were discovered, conducted between 1908 and 1913.