o beaute sans seconde SeuIe sembIabIe Ii toi SOLEIL pour tout Ie monde ... JEAN-FRANc;OIS SARASIN (1615-1654) The last decade has seen the publication of monographs covering most areas of solar activity: flares (Smith and Smith, 1963), sunspots (Bray and Loughhead, 1964) and the corona (Billings, 1966). Consequently, of all the major manifestations of solar activity only prominences are without a comprehensive and unified treatment in the current literature. The present book is written in an attempt to remedy this situation, and to furnish an account of some of the most spectacular and most beautiful aspects of solar activity. Our ultimate aim is an understanding of the physical processes involved. I hope that this book may provide if only a small step toward this goal. After an historical introduction and some general definitions Chapter I proceeds with an account of several classification schemes for prominences. Most of the observational material is presented in Chapter II and forms the basis on which different models of prominences are built in Chapter III. Chapters IV and V give most of the physics of prominences, treating, as they do, the formation and stability of these objects. The interaction of prominences with other manifestations of solar activity is the subject of Chapter VI, and the final Chapter VII considers prominences in the larger context: as an integral part of the corona.