The writings of Copernicus were unavailable in English until the publication of this 1939 translation from the original Latin. A three-part collection, it consists of the Commentariolus, Copernicus' sketch of his hypotheses for the heavenly motions; the Narratio prima, a popular introduction to Copernican theory; and the Letter against Werner, Copernicus' refutation of the views of a contemporary. This revised edition of the original English translation features extensive editorial apparatus, including an introduction with biographies of Copernicus and his disciple, George Joachim Rheticus, as well as background information on each of the treatises, an annotated bibliography, and an index. Unabridged republication of the second, revised 1959 edition.