Now in paperback, this book deals with the evolution of X-ray astronomy during the initial phases of its development. The story commences in the late 1950s with the discovery of high-energy radiations from beyond the solar system, and is taken through to the point at which X-ray astronomers began exploring questions of broader interest in astronomy. In examining this early period, when scientists acquired fundamental data and the rudiments of theory, the author shows how technical progress, and public policy changes played important roles in advancing the subject. Three transformations of astronomy as a discipline are highlighted: the augmentation of purely optical observations; the emergence of federal funding as the dominant source of financial support; and the greatly altered size and structure of the research community.