After Clarke's nonfiction science book "The Exploration of Space" (1951) was successfully received, he began to focus on his writing career. In February 1952, Clarke started working on the novelization of "Guardian Angel"; he completed a first draft of the novel "Childhood's End" in December, and a final revision in January 1953. Clarke travelled to New York in April 1953 with the novel and several of his other works. Literary agent Bernard Shir-Cliff convinced Ballantine Books to buy everything Clarke had, including "Childhood's End", "Encounter in the Dawn" (1953), (which Ballantine retitled "Expedition to Earth"), and "Prelude to Space" (1951). However, Clarke had composed two different endings for the novel, and the last chapter of "Childhood's End" was still not finished. Clarke proceeded to Tampa Bay, Florida, to go scuba diving with George Grisinger, and on his way there visited his friend Frederick C. Durant - President of the International Astronautical Federation from 1953 to 1956 - and his family in the Washington Metropolitan Area, whilst he continued working on the last chapter. He next traveled to Atlanta, Georgia, where he visited Ian Macauley, a friend who was active in the civil rights movement. Clarke finished the final chapter in Atlanta while Clarke and Macauley discussed racial issues; these conversations may have influenced the development of the last chapter, particularly Clarke's choice to make the character of Jan Rodricks – the last surviving member of the human species – a black man.