... History of astronomy written without the aid of manuscripts and other unpublished material would be immeasurably impoverished. ... The twentieth-century example centres on what has become known as ``The Great Debate'', a meeting at the Academy of Sciences in Washington on 26 April 1920 at which Harlow Shapley of Mount Wilson and Heber Doust Curtis of Lick gave talks on ``The Scale of the Universe''. ... Hoskin, M., Newton, Providence and the universe of stars, J. Hist. ...