The study of the internal structure of the stars would seem, at first thought, to be a singularly futile and unrewarding field of endeavor; it is difficult to imagine a more inaccessible spot than the interior of a star. This subject, however, is one of the classical topics in astrophysics, and it has attracted a continuous succession of outstanding astronomers and physicists. Although much of the theory of stellar structure is necessarily highly speculative, there have been some truly solid

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... ievements. Only a short time after Walter Adams obtained the necessarily poor spectroscopic observations of the companion of Sirius, which suggested an average density of the order of 50,000 for this white dwarf, the theory of a degenerate gas was worked out and successfully applied to (of all things) the behavior of electrons in metals at room temperatures. A short time later, studies of the structures of stars of various masses and luminosities strongly suggested that some kind of atomic-energy generation was taking place in these deep interiors, and thus made it almost inevitable that such processes would first be recognized, then evaluated in detail, and finally controlled and used. This volume, Stellar Structure (University of Chicago Press, Chicago, 1965. 668 pp., $17.50), edited by Lawrence H. Aller and Dean B. Mc-Laughlin, is the fifth to appear in a nine-volume compendium of astronomy and astrophysics, Stars and Stellar Systems, which is being published under the general editorship of Gerard P. Kuiper and Barbara M. Middlehurst. In this volume, 11 experts discuss, in 11 long chapters, the problems of internal structure, the sources of stellar energy, the origin of the chemical elements, observational and theoretical aspects of supernovae, the nature of magnetic stars, stellar stability, and stellar evolution and age determinations. Three of the 11. authors are products of the Indiana Univer-