Sydney Chapman (1888-1970) was arguably one of the greatest scientists of the twentieth century. His comprehensive work on the kinetic theory of gases and solar-terrestrial physics, as well as on the mechanisms behind the formation of Earth's ozone layer, has inspired a wide swath of research spanning several generations [Van Allen, 1970]. Chapman, a member of the Royal Society, in London, and president of the International Geophysical Year (IGY), also was a recipient of AGU's William Bowie Medal. Young AGU members today may recognize Chapman from the topical conferences that carry his name. Although his biography has so far not been published, he gave three talks on his life: two at the National Center for Atmospheric Research, Boulder, Colo., in 1965 and 1966, and one at the Geophysical Institute, University of Alaska Fairbanks, in 1967 (see Figure 1). All three are transcribed and included in a book, Sydney Chapman, Eighty: From His Friends [Akasofu et al., 1968]. These talks, combined with other sources, shed light on this insightful and discerning scientist.