Prominences are amazing objects of great beauty whose formation, basic structure and eruption represent one of the basic unsolved problems in Solar Physics. It is now 14 years since the last book on prominences appeared (Tandberg-Hanssen, 1974), during which time much progress in our knowledge of the physics of prominences has been made, and so the time is ripe for a new text book which it is hoped will be a helpful summary of the subject for students, postdocs and solar researchers. Indeed, the last few years has seen an upsurge in interest in prominences due to high resolution ground-and space-based observations and advances in theory. For example, an IAU colloquium was held in Oslo (Jensen et al, 1978), a Solar Maximum Mission Workshop took place at Goddard Space Right Center (poland, 1986), an IAU Colloquium is planned in Yugoslavia in September 1989 in prominences and it is expected that the SOHO satellite will be a further stimulus to prominence research. In November 1987 a Workshop on the Dynamics and Structure of Solar Prominences was held in Palma Mallorca at the invitation of Jose Luis Ballester with the aim of bringing observers and theorists together and having plenty of time for in-depth discussions of the basic physics of promi nences."

Helio- and asteroseismology study the interior of the Sun and other stars, by means of observations of oscillations on their surfaces. The last 10 years in the study of the solar interior, to a has witnessed a very rapid evolution point where we can now contemplate investigating the physical state of matter, or the details of rotation and other large-scale motion, in the Sun. The stellar studies are in some respects at the point of the solar studies 10 years ago, but appear poised to take off. Thus the time was deemed ripe for lAO Symposium No 123, to assess the present status of this work, and plan for its future development. Apart from the seismic data, few observations are available to provide information about stellar interiors. Detailed studies, by spectral analysis, can be made of stellar surface properties, including atmospheric temperature and chemical composition. However, the stellar radiative spectrum is almost entirely fixed by the mass, luminosity, radius and surface rotation of the star, and contains essentially no other information about the interior. An important test of stellar evolution theory is provided by observations of stel lar clusters, whose members can reasonably be assumed to have the same age and chemical composition. The location of such stars in a HR diagram, where luminosity is plotted against the effective temperature, can roughly be understood in terms of stellar evolution calculations."

In September 1984 a Summer School on Solar System Plasmas was held at Imperial College with the support of the Science and Engineering Research Council. An excellent group of lecturers was assembled to give a series of basic talks on the various aspects of the subject, aimed at Ph. D. students or researchers from related areas wanting to learn about the plasma physics of the solar system. The students were so appreciative of the lectures that it was decided to write them up as the present book. Traditionally, different areas of solar system science, such as solar and magnetospheric physics, have been studied by separate communities with little contact. However, it has become clear that many common themes cut right across these distinct topics, such as magnetohydrodynamic instabilities and waves, magnetic reconnect ion , convection, dynamo activity and particle acceleration. The plasma parameters may well be quite different in the Sun's atmosphere, a cometary tailor Jupiter's magnetosphere, but many of the basic processes are similar and it is by studying them in different environments that we come to understand them more deeply. Furthermore, direct in situ measurements of plasma properties at one point in the solar wind or the magnetosphere complement the more global view by remote sensing of a similar phenomenon at the Sun.

I have felt the need for a book on the theory of solar magnetic fields for some time now. Most books about the Sun are written by observers or by theorists from other branches of solar physics, whereas those on magnetohydrodynamics do not deal extensively with solar applications. I had thought of waiting a few decades before attempting to put pen to paper, but one summer Josip Kleczek encouraged an im mediate start 'while your ideas are still fresh'. The book grew out of a postgraduate lecture course at St Andrews, and the resulting period of gestation or 'being with monograph' has lasted several years. The Sun is an amazing object, which has continued to reveal completely unexpected features when observed in greater detail or at new wavelengths. What riches would be in store for us if we could view other stars with as much precision Stellar physics itself is benefiting greatly from solar discoveries, but, in tum, our understanding of many solar phenomena (such as sunspots, sunspot cycles, the corona and the solar wind) will undoubtedly increase in the future due to their observation under different conditions in other stars. In the 'old days' the solar atmosphere was regarded as a static, plane-parallel structure, heated by the dissipation of sound waves and with its upper layer expanding in a spherically symmetric manner as the solar wind. Outside of sunspots the magnetic field was thOUght to be unimportant with a weak uniform value of a few gauss."

The most complete guide to viewing eclipses—including details on every solar and lunar eclipse through 2017

Want to observe the most fleeting eclipse phenomena, take dramatic photos, and keep a detailed record of the experience? Now you can be prepared. This comprehensive one-stop resource covers everything you need to know about solar and lunar eclipses—why they happen, how to view them, how to photograph them, even when and where they will occur through the year 2017. Here's where to turn for:

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Traditionally, solar and stellar physics have been two separate branches of astronomy, which independently of each other have developed their own scientific goals and methods. During the last decade, however, we have witnessed a gradual convergence of these two areas: The solar physicists realize more and more that the sun has to be seen as a special case in a large family of stars of various properties. A more complete understanding of the sun can only be achieved by considering it in this broader context. The stellar physicists on the other hand have become aware that the detailed knowledge of the physical processes that the solar physicists have reached has a more general significance and can be applied to a variety of other astrophysical objects. Observational techniques developed in solar work can frequently be adapted for other stars as well. This unified approach to solar and stellar physics is often called the "solar-stellar connection." One main goal of this approach has been to understand the general nature and causes of stellar activity. The pioneering and visionary program to search for activity cycles on other stars started by Olin Wilson at the Mount Wilson Observatory 16 years ago has born fruit: in his sample of 91 stars, cyclic behaviour similar to that of the sun is found to be quite common, but many stars also show irregular activity fluctua.tions of large amplitude.

No part of the Hertzsprung-Russell diagram shows a more pronounced diversity of stellar types than the upper part, which contains the most luminous stars. Can one visualize a larger difference than between a luminous, young and extremely hot Of star, and a cool, evolved pulsating giant of the Mira type, or an S-type supergiant, or - again at the other side of the diagram - the compact nucleus of a planetary nebula? But there is order and unity in this apparent disorder! Virtually all types of bright stars are evolutionally related, in one way or the other. Evolution links bright stars. In many cases the evolution is speeded up by, or at least intimately related to various signs of stellar instability. Bright stars lose mass, either continuously or in dramatic sudden events, they vibrate or pulsate - and with these tenuous, gigantic objects this often happens in a most bizarre fashion. Sometimes the evolution goes so fast that fundamental changes are observable in the time span of a human's life - several of such cases have now been identified.

In Placing Outer Space Lisa Messeri traces how the place-making practices of planetary scientists transform the void of space into a cosmos filled with worlds that can be known and explored. Making planets into places is central to the daily practices and professional identities of the astronomers, geologists, and computer scientists Messeri studies. She takes readers to the Mars Desert Research Station and a NASA research center to discuss ways scientists experience and map Mars. At a Chilean observatory and in MIT's labs she describes how they discover exoplanets and envision what it would be like to inhabit them. Today's planetary science reveals the universe as densely inhabited by evocative worlds, which in turn tells us more about Earth, ourselves, and our place in the universe.

1. 1. Short History of Solar Radio Astronomy Since its birth in the forties of our century, solar radio astronomy has grown into an extensive scientific branch comprising a number of quite different topics covering technical sciences, astrophysics, plasma physics, solar-terrestrial physics, and other disciplines. Historically, the story of radio astronomy goes back to the times of James Clerk Maxwell, whose well known phenomenological electromagnetic field equations have become the basis of present-time radio physics. As a direct consequence of these equations, Maxwell was able to prognosticate the existence of radio waves which fifteen years later were experimentally detected by the famous work of Heinrich Hertz (1887/88). However, all attempts to detect radio waves from cosmic objects failed until 1932, which was mainly due to the early stage of development of receiving techniques and the as yet missing knowledge of the existence of a screening ionosphere (which was detected in 1925). Therefore, famous inventors like Thomas Edison and A. E. Kennelly, as well as Sir Oliver Lodge, were unsuccessful in receiving any radio emission from the Sun or other extraterrestrial sources. Another hindering point was that nobody could a priori expect that solar radio emission should have something to do with solar activity so that unfortunately by chance some experiments were carried out just at periods of low solar activity. This was also why Karl Guthe Jansky at the birth of radio astronomy detected galactic radio waves but no emission from the Sun.

For over 35 years, radio astronomical techniques have made an impressive series of advances in our understanding of solar phenomena. However, although the subject has been partially discussed in "Paris Symposium on Radio Astronomy" in 1958, NASA-GSFC Symposium on "Physics of Solar Flares" in 1963, and the lAU Symposium No. 57 on "Coronal Disturbances" in 1973, there has not been a major international meeting dedicated to "Radio Physics of the Sun." This is the first major symposium on the subject held under the auspices of the International Astronomical Union. It was jointly spon sored by lAU Commission 40, Radio Astronomy, and by lAU Commission 10, Solar Activity. It was also sponsored by the Solar Physics Division of the American Astronomical Society. Thig volume contains the proceedings of this meeting, lAU Symposium No. 86 on "Radio Physics of the Sun" that was held in College Park, Maryland, August 7-10, 1979. The Scientific Organizing Committee of the Symposium consisted of M. R. Kundu (chairman), G. A. Dulk, O. Hachenberg, M. Kuperus, D. J. McLean, D. Melrose, M. Pick, J. L. Steinberg, T. Takakura, A. Tlamicha and V. V. Zheleznyakov. The topics and speakers were chosen in order to emphasize the current observational material with particular reference to centi meter wavelength observations of a few arc-second resolution, fast two-dimensional pictures of the sun at meter-decameter wavelengths and the recent advances in plasma and radiation theory."

Jan H. Dort's work Ad: r>iaan Blaauw Meritus Emeritus Harry van der Laan 21 Jan Hendrik Dort and Dutch astronomy H. G. van Bueren 31 Dort's scientific importance on a world-wide scale Bengt Stromgren 39 Gart and international co-operation in astronomy D. H. Sadler 45 Reminiscences of the early nineteen-twenties Peter Van de Kamp 51 The first five years of Jan Dort at Leiden, Bart J. Bok 1924-1929 55 Early galactic structure Per Olof Lindblad 59 Early galactic radio astronomy at Kootwijk C. A. Muller 65 W. N. Christiansen Dort and his large radiotelescope 71 Ten years of discovery with Dort's Synthesis Radio Telescope R. J. Allen and R. D. Ekers 79 Gort's work on comets Maarten Schmidt 111 The evolution of ideas on the Crab Nebula L. WoUjer 117 Gort's work reflected in current studies of galactic CO W. B. Burton 123 On high-energy astrophysics V. L. Ginzburg 129 Dort and extragalactic astronomy Margaret and Geoffrey Burbidge 141 Birthday wishes John A. and Janette Wheeler 151 The Earth and the Universe Abraham H. Oort 153 The challenge of Jan Dort J. H. Bannier 157 Jan Dort at the telescope Fjeda Walraven 161 Gart Westerhout Personal recollections 163 Style of research Henk van de Hulst 165 Manuscript Jan H.

Double and multiple stars are the rule in the stellar population, and single stars the minority, as the abundance of binary systems in the space surrounding the sun shows beyond doubt. Numerous stellar features, and methods of their exploration, ensue specifically from the one but widespread property, the binary nature. Stellar masses are basic quantities for the theory of stellar structure and evolution, and they are ob tained from binary-star orbits where they depend on the cube of observed parameters; this fact illustrates the significance of orbits as well as the accuracy requirements. Useful in dating stellar history is the knowledge that components of a system, different though they may appear, are of the same origin and age. Between star formation and the genesis of binaries a direct connection can be traced. The later stages of stellar life branch into a great variety as mutual influence between the components of a close binary pair develops. Transfer and exchange of mass and the presence of angular momentum in the orbit give rise to special tracks of evolution, not found for single stars, and to peculiar spectral groups. This is not a new story but it has a new ending: The patterns of evolution involving mass transfer appear to lead ultimately to single objects."

This book provides readers with an understanding of the basic physics and mathematics that governs our solar system. It explores the mechanics of our Sun and planets; their orbits, tides, eclipses and many other fascinating phenomena. This book is a valuable resource for undergraduate students studying astronomy and should be used in conjunction with other introductory astronomy textbooks in the field to provide additional learning opportunities. Features: Written in an engaging and approachable manner, with fully explained mathematics and physics concepts Suitable as a companion to all introductory astronomy textbooks Accessible to a general audience

Our first attempt to organize a Symposium on solar activity was made at the lAO General Assembly in Brighton 1970. There, at the session of Commission 10, we proposed to organize a Symposium which would stress the observational aspects of solar activity. It was our hope that such a Symposium might stimulate studies of those important problems in solar physics which for a long time had been neglected in overall scientific discussion. Although a provisional date for the Symposium was then decided, it did not take place to avoid overlapping with other lAO activities. At the session of Commission 10 in Sydney -on the occasion of the XVth lAO General Assembly in 1973 -we repeated our proposal and forwarded the invitation of the Czechoslovak Academy of Sciences to organize the Symposium in Prague. Both were accepted. During the discussions about the programme of the Symposium -enthusiastically promoted by the late president of Commission 10, Prof. K. O. Kiepenheuer -it was decided to change slightly its subject. The theoreti cal problems were stressed and the majority of the Scientific Organizing Committee agreed not to deal with short-lived phenomena of the solar activity or with individual active regions. Symposium No. 71 was held in Prague from August 25 to August 29, 1975. Its Organizing Committee consisted of V. Bumba (Chairman), W. Deinzer, R. G. Giovanelli, R. Howard, K. O. Kiepenheuer, M. Kopecky, T. Krause, M. Kuperus, G."

This book is the first part of the originally planned publication by Z. Svestka and L. D. de Feiter 'Solar High Energy Photon and Particle Emission'. The second part, with the original title, was to be published by de Feiter in about one year from now. However, to the deep sorrow of all of us, Dr de Feiter died suddenly and unexpectedly when the present book was in print. Thus, unfortunately, de Feiter's second part may not appear. Due to the fact that the originally planned publication was divided into two parts, the present book is mainly descriptive and concerned with the flare morphology. It was expected that theoretical interpretations would be extensively developed in the second part, prepared by de Feiter. In particular, this refers to the theoretical back grounds of radio emissions, particle acceleration and particle propagation in space. Only in Chapter II, concerning the 'low-temperature' flare, do we go deeper into the theoretical interpretations, anticipating that de Feiter would have been concerned mainly with the 'high-energy' physics. Still, the book includes discussions on all important aspects of flares and thus can present the reader with a complete picture of the complex flare phenomenon. It is clear that many observed data on flares can be interpreted in different ways."

This monograph is based on four papers which have been published in Astrophysics and Space Sciences 1970--1974. They contain the results of our joint work started in 1968 at the University of California, San Diego, in La Jolla. The work was based on the belief that the complicated processes by which our solar system was formed can only be clarified by close collaboration between representatives of the physical and chemical sciences. Our investigations have also been strongly supported by work at other institu tions, especially by a group at the Royal Institute of Technology, Stockholm, where a number of plasma experiments have been made in order to clarify basic processes which are relevant to cosmogonic problems. These experiments were, in their turn inspired by theoretical work on primordial processes carried out during the last thirty-five years. We especially want to acknowledge the contributions by Drs N. Herlofson, B. Lehnert, C.-G. Fiilthammar, and Lars Danielsson in Stockholm and by Drs J."

The symposium on 'Solar Gamma-, X- and EUV Radiation' was held at Buenos Aires, Argentina, from 11 June to 14 June 1974. It was sponsored jointly by the Inter- national Astronomical Union (IAU) and the Committee on Space Research (COSPAR). The Organization Committee responsible for the program consisted of Drs K. A. Anderson (Chairman), J. L. Culhane, G. Elwert, B. B. Fossi, S. L. Mandel- s'tam, W. M. Neupert, V. K. Prokofiev, and J. Sahade and representatives of COSPAR, Drs H. Friedman and Z. Svestka. During the symposium Dr Svestka kindly represented the chairman of the Organizing Committee who was unable to attend the symposium. The local arrangements in Buenos Aires were made by Drs J. Sahade (Chairman), H. S. Ghielmetti, M. J. Gulich, H. Molnar, J. J. Tasso and N. Martinez Riva de Tropper. This symposium brought together the observational and theoretical aspects of the Solar Gamma-, X-, and EUV Radiation and other related solar emissions such as radio and energetic particles. There were three specific topics for the symposium, viz.

The idea of a symposium devoted to the contemporary knowledge of the world of Copernicus - the planetary system - to commemorate the 500th anniversary of his birth, came during the XIV General Assembly of IAU in Brighton. The Executive Committee has approved it in the program of the Extraordinary (Copernicus) General Assembly ofIAU in Poland in 1973. The IAU Symposium No 65 (Copernicus Symposium IV) on the 'Exploration of the Planetary System' was held in Copernicus' native town - Torun, Poland, from 5th to 8th September, 1973 under the auspices of Commissions 16 (Physical Study of Planets and Satellites) and 40 (Radio-astronomy) and the co-sponsorship of COSPAR. There were about 140 invited participants from 29 countries and about the same num ber of other participants to the Extraordinary General Assembly of IAU who came to Torun to attend the sessions of this symposium. Special funds of the Polish Acade my of Sciences made possible the participation of several young astronomers in this meeting. We are very grateful to Professor P. Swings, the Director of the Astrophysical Institute of the University of Liege, Belgium, for accepting the task of chairing this symposium. His expert and enthusiastic guidance helped us constantly in the prepara tion. The efforts of the Members of the Scientific Organizing Committee are also very much appreciated. Special thanks are due to Professors A. Dollfus and T. Owen."

This Symposium was held at Surfer's Paradise, Queensland, Australia, from 7 to 11 September 1973. The Organizing Committee, chaired by J. P. Wild, consisted of A. Boischot, A. Bruzek, J. T. Jefferies, G. Newkirk, T. Takakura, and V. V. Zhelez nyakov. We are indebted to the Local Organizing Commettee, chaired by S. F. Smerd and including R. G. Giovanelli, R. E. Loughhead, N. G. Seddon, K. V. Sheridan, and J. P. Wild, for advice in preparing this volume as well as for the smooth arrangement of the sessions. In addition, the session chairmen and reporters are to be thanked for their assistance in preparing the recorded discussions. It is a pleasure to thank Mrs R. Toevs and Mr A. Csoeke-Poeckh of High Altitude Observatory for assistance in editing these Proceedings. The financial aid for the Symposium afforded by the International Astronomical Union, the Ian Potter Foundation of Melbourne, and the Sunshine Foundation of Melboume, as well as generous assistance of the CSIRO Divisions of Physics and Radiophysics is gratefully acknowledged. That the solar corona is not a quiescent plasma was first fully appreciated through the discovery of solar radio bursts thirty years ago. Since that time intensive re search has uncovered a vast variety of coronal disturbances and revised our con cept of this region of the solar atmosphere to that of a dynamic medium undergoing continuous expansion, constantly evolving under the influence of underlying photo spheric activity, and frequently traversed by transient phenomena.

The IAU Symposium No. 62, 'The Stability of the Solar System and of Small Stellar Systems' was held in Warsaw in Poland during the Extraordinary General Assembly of the IAU in commemoration of the SOOth anniversary of the birth of Nicolaus Copernicus. The Symposium was sponsored by Commission 7 (Celestial Mechanics) and cosponsored by Commissions 4 (Ephemerides) and 37 (Star Clusters and Asso- ciations) of the IAU and by IUTAM. The Organizing Committee included Y. Kozai (Chairman), J. A. Agekjan, A. Deprit, G. N. Duboshin, S. G\lska (Local represen- tative), M. Henon, B. Morando and C. Parkes (IUTAM representative). The Symposium was supported financially by the IA U, the IUT AM and the Polish Academy of Sciences. Y. KOZAI Chairman of the Organizing Committee STABILITY THEORY IN CELESTIAL MECHANICS J MOSER Courant Institute of Mathematical ScIences, New York University, New York, N. Y. 10012, U.S.A. Abstract, This expository lecture surveys recent progress of the stability theory in Celestial Mechanics with emphasis on the analytical problems. In particular, the old question of convergence of perturbation series are discussed and positive results obtained, in the light of the work by Kolmogorov Arnold and Moser. For the three body problem, classes of quasi-periodic solutions and doubly asymptotic (or homo- clinic) orbits are discussed.

Over the past two decades auroral science has developed from a somewhat mysterious and imprecise specialty into a discipline central in the study of the ionosphere and magnetosphere. The investigation of aurora unites scientists with very different backgrounds and interests so that it is difficult to write a self-contained account of the field in a book of reasonable length. In this work I have attempted to include those aspects of theory which I have found valuable in predicting the effects on the atmosphere of auroral particle precipitation. In addition I have attempted to describe the techniques of observation with particular emphasis on optical methods which have been useful. While the aeronomy of aurora has been regarded as central, the mechanisms by which particles are accelerated and precipitated into the atmosphere is of no less interest. This aspect of the subject has however been treated in a briefer fashion since it is a part of the immense and rapidly developing field of magnetospheric science. Generally I have attempted to provide a coherent introduction to auroral science with an emphasis on relatively simple physical interpretations and models. References are given to enable the reader to find more extensive or rigorous discussions of particular topics. A fairly complete, quantitative atlas of the auroral spectrum is included.

It was about fourteen years ago that some of us became intrigued with the idea of searching the sky for X-ray and gamma-ray sources other than the Sun, the only celestial emitter of high-energy photons known at that time. It was, of course, clear that an effort in this direction would not have been successful unless there occurred, somewhere in space, processes capable of producing high-energy photons much more efficiently than the processes responsible for the radiative emission of the Sun or of ordinary stars. The possible existence of such processes became the subject of much study and discussion. As an important part of this activity, I wish to recall a one-day conference on X-ray astronomy held at the Smithsonian Astrophysical Observatory in 1960. The theoretical predictions did not provide much encouragement. While several 'unusual' celestial objects were pin-pointed as possible, or even likely, sources of X-rays, it did not look as if any of them would be strong enough to be observable with instru mentation not too far beyond the state of the art. Fortunately, we did not allow our selves to be dissuaded. As far as I am personally concerned, I must admit that my main motivation for pressing forward was a deep-seated faith in the boundless re sourcefulness of nature, which so often leaves the most daring imagination of man far behind."

The aim of the present book will be to summarize the results of the space exploration of the Moon in the past fifteen years -culminating in the manned Apollo missions of 1969-1972 -on the background of our previous acquaintance with our satellite made in the past by astronomical observations at a distance. Astronomy is one of the oldest branches of science conceived by the inquisitive human mind; though until quite recently it had been debarred from the status of a genuine experimental science by the remoteness of the objects of its study. With the sole exception of meteoritic matter which occasionally finds its way into our labora tories, all celestial bodies could be investigated only at a distance: namely, from the effects of attraction exerted by their mass, or from the ciphered messages of their light carried by nimble-footed photons across the intervening gaps of space. A dramatic emergence oflong-range spacecraft -capable of carrying men with their instruments not only outside the confines of our atmosphere, but to the actual surface of our nearest celestial neighbour - has since 1957 thoroughly changed this time honoured picture. In particular (as we shall detail in Chapter 1 of this book) space astronomy ofthe Moon is barely 15 years old. But relative infant as it is by age, it has already provided us with such a tremendous amount of new and previously inacces sible scientific data as to virtually revolutionalize our subject."

The devotion of an IA U symposium entirely to the topic of chromo spheric fine structure at a time when models of the spherically symmetric chromosphere are still evolving constitutes a valid recognition of the growing feeling among solar astron omers that the chromosphere cannot be understood independently of its discrete structural features. Network structure, which seemingly borders the photospheric supergranule cells, persists intact throughout the chromosphere and most of the chromosphere-corona transition region. The network is the locus of the bright coarse mottles, and the spicule bushes and is the terminus for one end of the quiet chromo spheric fibrils as well. Additionally, it is the locus of most of the magnetic flux of the quiet chromosphere. It is not surprising, therefore, that current studies of the chromosphere tend to center around efforts to better describe the network phenom ena and to ascertain the physical properties of the network features. Clearly, the supergranule cells and associated network structures constitute a fundamental and singularly important feature of solar structure in the boundary layers. Just as it is now clear that much of the chromo spheric fine structure is associated with the network bordering supergranule cells, it seems equally clear that structural features are almost universally associated with both fluid flow and magnetic geometry. Indeed, many observers claim that the brightness features faithfully map the mag netic lines offorce while still others claim that associated with each class of brightness feature there is a more or less unique fluid flow."

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.