Francis Aston (1877-1945), British physicist and Nobel laureate. Having discovered that neon had two isotopes, or possible molecular weights, Aston invented the mass spectrograph. This device allowed him to identify the isotopes present in a substance. His technique led him to discover 212 naturally-occurring isotopes, and won him the 1922 Nobel Prize in Chemistry. He also described the Whole Number Rule, or theory that all nuclei have weights that are whole-number multiples of 1/16th of the oxygen-16 isotope. This portrait is from the Bain News Service, one of America's oldest news picture agencies, which holds images dating from the 1890s to the 1930s.