IAU Symposium 103 was held at University College London, August 9-13 1982. This volume contains the proceedings of the meetin- invited papers, abstracts of contributed papers, and discussion. As is nON custanary with the proceedings of IAU Symposia, the manuscript was canpiled fran camera-ready copy. The Editor was responsible for the preparation of the abstracts of the contributed papers and the discussion, the authors of the invited papers for the preparation of their 0Nn reviews. The discussion at the meeting was lively and infonnative, and the Editor hopes that a reasonably faithful and readable record of the discussion is to be found in these proceedings. In accordance with the wish of the Scientific Organising Committee, an object index has been canpiled and appended. It is to be hoped that the index will augment the usefulness of the volune. The Editor is greatly indebted to M. J. Barlow for his help in preparing the index. Financial assistance for the meeting was provided by the IAU and University College London. The hospitality received during the excursion to the Old Royal Observatory and National Maritime MUseum, Greenwich, is gratefully acknowledged. The task of editing these proceedings has been greatly facilitated by the excellent secretarial assistance of V. A. Kerr. David Flower Durham, October 1982 xiii D. R. Flower (ed.), Planetary Nebulae, xiii.

It was particulary appropriate that the IAU Symposium N 100 be held in Besan~on in 1982 (August 9-13), since this coincided with the 100th anniversary of the Observatoire de Besan~on. The meeting was held on the campus of the Universite de Franche-Comte and was sponsored by IAU commission 28 and co-sponsored by commissions 33 and 40. It was organized under the auspices of the Ministere de l'Education Nationale, the Centre National de la Recherche Scientifique and the Institut National d'Astronomie et de Geophysique. It was attended by 166 scien- tists from 22 countries. The subject of the symposium was internal kinematics and dynamics of galaxies and it was aimed to confront recent theoretical developments in this field with the wealth of new observational mate- rial obtained during the last few years. Barred galaxies and spiral structure were two major topics, though unfortunately at the last minute the main proponent of one of the spiral formation theories was unable to attend. The program included 23 reviews, 53 contributions and 39 poster papers, and there was ample time for discussion.

The Origin and Evolution of Galaxies is the outstanding problem of modern cosmology. Fortunately. we have a firm cosmological framework on which to base our theories (the hot big bang) and recently there has been substantial progress in providing observations which potentially can constrain these theories. The problem of galaxy formation is. as a consequence. one involving many diverse branches of physics and astrophysics. It has been the aim of the school. and this compendium of lectures and seminars. to bring together these diverse aspects at a level enabling research workers to understand what is going on in other corners of the subject and to see how progress in each area impinges on the others. We are grateful to the contributors to this volume for allowing us considerable editorial license with their articles. We have attempted to provide a representative sample of the talks that were given at the school besides the texts of the invited lecturers. It is regrettable that for reasons of space we have had to leave out a number of other contributions.

continues to be extremely rewarding. Experiments on future missions, such as the two 1981 Veneras, Gamma Ray Observatory, and the International Solar Polar Mission, will undoubtedly provide new and unexpected discoveries, but the work of the Leningrad group is likely to remain an important contribution to the field for some time to come. c.E.S.R. KEVIN HURLEY Toulouse, France June 9, 1981 CATALOG OF COSMIC GAMMA-RAY BURSTS FROM THE KONUS EXPERIMENT DATA Parts I and II E. P. MAZETS, S. V. GOLENETSKII, V. N. IL'INSKII, V. N. PANOV, R. L. APTEKAR, YU. A. GUR'YAN, M. P. PROSKURA, 1. A. SOKOLOV, Z. Y A. SOKOLOV A, and T. V. KHARITONOV A A. F. Ioffe Physical-Technical Institute, U.S.S.R. Academy of Sciences, Leningrad, U.S.S.R. and A. V. DYATCHKOV and N. G. KHAVENSON Institute of Cosmic Research, U.S.S.R. Academy of Sciences, Moscow, U.S.S.R. (Received 2 July, 1980) Abstract. Data are presented on the temporal structure, fluxes, energy spectra and coordinates of the sources of gamma-ray bursts detected in the KONUS experiment on Venera 1 I and Venera 12 space probes in the period September 1978 to May 1979. The statistical distributions of gamma bursts in duration, intensity, and peak power, as well as the distribution of the burst sources over the celestial sphere presented are based on the updated KONUS information obtained until February 1980.

Our knowledge of the distribution and properties of the small solid particles within the solar system continues to improve rapidly. Much of the progress is due to observations from spacecraft which offer completely new locations from which to view phenomena such as the zodiacal light. In combination with ground-based observations and improved theoretical models, a picture now emerges with a clarity un attainable even a few years ago. The need for a survey of the situation was recognized in 1976 and, at meetings of COSPAR and the International Astronomical Union in that year, planning began for a symposium to be held in 1979 at a time and place convenient for those attending the IAU General Assembly in Montreal. The result was IAU Symposium No. 90, "Solid Particles in the Solar System," held at the University of Ottawa, from August 27 to 30, 1979. This volume includes eleven invited papers intended to survey par ticular areas of the overall subject and numerous contributed papers providing more detail on specific problems. We hope the combination will prove valuable to both the general reader interested in the current picture of the particles in interplanetary space and also to the specialist involved in research in the field."

Symposium No. 88 of the International Astronomical Union was devoted to a comprehensive review of all types of close.binary stars. The nine sessions were organized according to the type of the objects to be discussed. We have preserved this system, but assembled twelve papers of a more general character (reviews and surveys) into a special chapter placed at the beginning of this book. We would like to remind the reader that the Symposium was preceded by the IAU Colloquium No. 53 on White Dwarfs and Variable Degenerate Stars , and that the sessions on Cataclysmic Variables and related topics at the two meetings supplemented each other. The discussion in Toronto was carefully recorded by Mr. Robert Gauthier. We also wish to thank Mr. Robert O'Daniel, Ms. Joan Kaufmann, and Ms. Linda Reimers for assisting us with the editorial work. M. J. Plavec D. M. Popper R. K. Ulrich ACKNOWLEDGEMENTS The International Astronomical Union and the University of Toronto contributed substantial funds enabling a number of participants to receive travel grants. The Symposium was sponsored by the following Commissions of the International Astronomical Union: 29 (Stellar Spectra), 30 (Radial Velocities), 35 (Stellar Structure), 42 (Close Binary Stars), and 44 (Astronomy from Space). Our special thanks go to the members of the Scientific Organizing Committee. The Symposium was attended by 170 participants from 26 countries.

IAU Symposium No. 82, "Time and the Earth's Rotation," met to discuss modern research in the field of the rotation of the Earth with particu lar emphasis on the role of new observational techniques in this work. The use of these techniques has prompted a new look at the definitions of the traditional reference systems and the concepts of the rotation of the Earth around its center of mass. Specific topics discussed were time, polar motion, reference systems, conventional radio interferometry, very'long baseline interferometry (VLBI), Doppler satellite methods, satellite laser ranging, lunar laser ranging, and geophysical research concerning the Earth's rotation. Improvement in the accuracy of the observations is a key to possible solutions of the many unsolved problems remaining in this field. It appears that such improvement, using both classical and new techniques, is forthcoming in the near future. This will surely contribute to a better understanding of some of the long-standing questions concerning the rotation of the Earth around its center of mass and lead to an improved knowledge of the rotating, deformable Earth. This volume contains the papers presented at IAU Symposium No. 82 as well as the discussions provoked by these papers. It is hoped that it captures the principal points of the meeting and that it will contribute not only to a better understanding of existing problems, but also to future research in time and the Earth's rotation."

The organization of this Symposium had its beginnings at the International Astronomical Union General Assembly in Grenoble in 1976. The initial "rounding up" of the Scienti fic Organizing Committee was begun by Drs. Snow and Swings; most of us who became the eventual organizing committee met a few times during the Assembly and formulated the essential outlines of the meeting. Extensive correspondence with all the committee subsequently established the program. The idea was to bring together both observers and theoreticians to discuss the stellar winds and mass loss rates and their effects on evolutions of O-type stars. On the observational side, there are now spectroscopic data from the far UV to the near IR regions concerning the stellar winds. There is also information about the free-free emission in the wind from the IR and radio portions of the spectrum. Fortunately, these different detection methods give more or less the same mass loss rate for the one star, s Pup" which has been observed at all wavelengths. One of the intents of the first three sessions of this Symposium is to outline the eXisting data on mass loss rates as it per tains to the O-type stars."

Proceedings of IAU Symposium No. 76 held at Cornell University, Ithaca NY, USA, 6-10 June 1977

Richly illustrated with a luminous and informative collection of maps, photographs, and graphics, this atlas is the perfect companion for exploring the wonders of the universe as viewed from Earth. This expansive illustrated atlas invites readers to roam the night sky for constellations, planets and moons, eclipses, comets and meteor showers, auroras, and deep-sky treasures including nebulae and galaxies-many visible to the naked eye and all with binoculars or a backyard telescope. Beginning with basic space science and including a complete set of night sky maps for all four seasons in the Northern and Southern Hemispheres, this fascinating book guides the reader toward the most rewarding observations. A unique chapter on astro-tourism highlights ancient observatories, dark-sky preserves, and other global destinations for the sky-seeking traveller; a final chapter details current and future space missions and what they might discover. Richly illustrated with awe-inspiring imagery-including photos from space missions and telescopes, science-based artists' interpretations, and explanatory graphics-the book also contains 170 maps and charts of planets, moons, and constellations, from Earth's moon to moons of Saturn. Practical advice throughout helps readers see what they have been reading about, building key observational skills such as "star hopping" from easy-to-find stars to fainter deep-sky objects and focusing on "deep sky treasures:" areas rich in observable phenomena. Approachable and authoritative, gorgeous and fascinating, this large-format illustrated atlas will intrigue all who love to gaze up in wonder at the night sky-and find themselves wanting to know more.

Proceedings of IAU Symposium No. 75 held in Geneva, Switzerland, September 6-10, 1976. Dedicated to Solomon Pikel'ner

IAU Symposium No. 80, The HR Diagram - The 100th Anniversary of Henry Norris Russell was held on November 2-5, 1977 at the National Academy of Sciences in Washington D. C. , in order to commemmorate the birth of Henry Norris Russell on October 25, 1877 and to review current problems in the use of the Hertzsprung-Russell diagram. The IAU has sponsored two previous conferences concerned mainly with the HR diagram; The Position of Variable Stars in the Hertzsprung-Russell Diagram, a colloquium held at Bamberg in 1965 and The Hertzsprung Russell Diagram (IAU Symposium No. 10, J. L. Greenstein, ed. ) held in Moscow in 1959. In 1974 a conference, Multicolor Photometry and the Theoretical HR Diagram (Dudley Obs. Report No. 9, A. G. D. Philip and D. S. Hayes, eds. ) was held in Albany, N. Y. ; and in 1964 a conference, Basic Data Pertaining to the Hertzsprung-Russell Diagram, was held at the Flagstaff Station of the U. S. Naval Observatory in honor of Ejnar Hertzsprung and to dedicate the 61-inch astrometric reflector. (Vistas in Astronomy Vol. ~, A. Beer and K. Aa. Strand, eds. , Pergamon Press, Oxford). Volume 12 of Vistas in Astronomy, The Henry Norris Russell Memorial Volume (1970), contains a review paper on Changing Interpretations of the Hertzsprung-Russell Diagram 1910-1940, A Historical Note by B. W. Sitterly.

Symposium No. 73 of the International Astronomical Union was devoted to the obser vational and theoretical aspects of close binary stars. Just over 100 participants attended. The Local Organizing Committee would like to thank the following: IAU for travel grants. IBM United Kingdom Ltd for very generous support in the form of travel grants. The Royal Society for the provision of travel grants to participants from Eastern Europe. We also thank the Director of the Institute of Astronomy, and our colleagues and research students for their moral support and assistance. Finally we thank Pauline Haughey for assisting with the editorial work. PETER EGGLETON SIMON MITTON JOHN WHELAN SCIENTIFIC ORGANIZING COMMITTEE M. Plavec (Chairman), T. Herczeg, E. P. J. van den Heuvel, J. B. Hutchings, G. Larsson-Leander, L. B. Lucy, L. Mestel, B. Paczynski, J. Sahade, B. Warner, R. E. Wilson. LOCAL ORGANIZING COMMITTEE J. A. J. Whelan (Chairman), P. P. Eggleton, S. A. Mitton LIST OF PARTICIPANTS Baldwin, B. W., Victoria, Canada Icke, V., Cambridge, England Bateson, F. M., Tauranga, New Zealand Koumsiachvilli, M., Moscow, U.S.S.R Bath, G. T., Oxford, England Krzeminski, W. A., Warsaw, Poland Batten, A. H., Victoria, Canada Larsson-Leander, G., Lund, Sweden Berthier, E. J., Paris, France Leung, K.-C., Nebraska, U.S.A."

The International Astronomical Union Symposium No. 70 on Be and Shell Stars, the Merrill-McLaughlin Memorial Symposium, was held in Bass River (Cap Cod), Massachusetts, U. S. A. , from September 15th through 18th, 1975. Fifty-three astronomers from Argentina, Belgium, Canada, Czechoslovakia, France, Israel, the United Kingdom, the United States, and the Vatican attended and participated in the Symposium. This volume, which parallels the actual program closely, contains the papers presented at the Symposium plus most of the discussion following the papers. New observational techniques and fresh theoretical ideas have resulted over the past few years in a renewed interest in Be and shell stars. At IAU Symposium No. 51 on Extended Atmospheres and Circumstellar Matter in Spectroscopic Binary Sys tems, the Otto Struve Memorial Symposium, in Parksville, British Columbia, Canada, three years ago, a number of participants expressed the wish to organize a symposium on Be and shell stars. If we wish to identify an official 'Father of IAU Symposium No. 70', it would be Mirek Plavec who, in his capacity as President of IAU Commission 42 (Photometric Double Stars) requested and received the cooperation of Commissions 29 (Stellar Spectra) and 36 (Stellar Atmospheres), suggested an Organizing Committee, and wrote to the IAU General Secretary in 1973 requesting that the IAU Executive Committee approve the proposed confer ence as an IAU Symposium.

The general discussions of the roles of photometric and spectroscopic classification at Cordoba in 1971 (lAU Symposium No. 50), and of the calibration of classification indices at Geneva in 1972 (IAU Symposium No. 54), revealed clearly the steadily in creasing importance of abundance parameters. The multipliCity of these, however, raised so many new problems that it was logical that the 1975 meeting at Lausanne should be concerned with ways in which differences in abundance affect both spectral types and photometric indices. Commissions 29 and 36 joined with Commission 45 in sponsoring this Symposium. Since the date of the meeting came shortly after the formal retirement of Professor William W. Morgan from the University of Chicago, it was quickly agreed that this meeting should be dedicated to him in recognition of his unique contributions to spectral classification. In the opening paper of the Symposium Dr. Bengt Stromgren has summarized these. To his remarks we should add only that it was about 1940 that Morgan first distinguished the group of G- and K-type stars with weak CN bands and metallic lines - stars which have since been recognized as having the abundance of all metals relative to hydrogen much lower than in stars of the solar population. Spectra of two of these, HD 81192 (Boss 2527) and 8 Lep, were later shown as examples of the group in the Yerkes Atlas of 1943."

The idea of holding this Symposium has its origin in a conversation with G. Con to poulos during the winter of 1973. It was then clear that the progress realized in Stellar Dynamics since the Thessaloniki symposium had given a new shape to the field. Other meetings such as the C. N. R. S. colloquium held in Paris in 1967 or the LA. V. colloquium held in Cambridge, England, in 1970 had in the meantime given opportunities to review the advances achieved in several branches of this field. We thought that time had come to organize a general confrontation of the new results obtained in the approach of the gravitational N-body problem by different methods, in the investigation of spherical and flattened systems, in the comparisons with ob servations and in more theoretical speculations on orbits, integrals of motion, dense nuclei or relativistic stellar dynamics. Things were made easy by the support of Commissions 33 and 37 which welcomed the proposition and by 1. R. King who accepted to act as Chairman of the Scientific Organizing Committee. The final decision to meet in Besan'Yon was taken during the XVth General Assembly of the LA. U. in Sydney in August 1973. The members of the Organizing Committee were: 1. R. King (Chairman), G. Con topoulos, A. Hayli, M. Henon, G. Hori, D. Lynden-Bell, L. Perek, L. Spitzer, R. Wielen, Ya. Zel'dovich while the members of the Local Committee were: A."

This book contains a set of articles based on a session of the annual meeting of the American Association for the Advancement of Science held in San Francisco in February, 1974. The reason for the meeting arose from the need to communicate to the largest possible scientific community the dramatic advances which have been made in recent years in the understanding of collapsed objects: neutron stars and black holes. Thanks to an unprecedented resonance between X-ray, y-ray, radio and optical astronomy and important new theoretical developments in relativistic astro physics, a new deep understanding has been acquired of the physical processes oc curring in the late stages of evolution of stars. This knowledge may be one of the greatest conquests of man's understanding of nature in this century. This book aims to give an essential and up-to-date view in this field. The analysis of the physics and astrophysics of neutron stars and black holes is here attacked from both theoretical and experimental points of view. In the experimental field we range from the reviews and catalogues of galactic X-ray sources (R. Gursky and E. Schreier) and pulsars (E. Groth) to the observations of the optical counter part of X-ray sources (P. Boynton) to finally the recently discovered gamma-ray bursts (I. Strong) and pulse astronomy R. B. Partridge)."

Colloquia and symposia have almost become a tradition among the variable-star astronomers; those held more or less regularly at Bamberg and Budapest have become well known. For a change, this time the organizing committee of Commission 27 decided to hold an LA. U. symposium in Moscow and to adopt as a special topic the relation between variable stars and the evolution of stars and stellar systems. This symposium, No. 67 in the LA. U. series, was prepared by two committees, a by B. V. Kukarkin, and a local one with V. A. Ambartsumian scientific one chaired as chairman, and G. S. Khromov as executive secretary. It was held in Moscow at the Physical and Astronomical Institutes of the Lomonosov University from July 29 to August 4, 1974. The symposium was opened with three short welcoming speeches by V. A. Ambartsu mian, J. M. Ternov (vice-rector of Moscow University), and B. V. Kukarkin. All three stressed the importance of the study of variable stars in connection with the evolution of stars and stellar systems, the role of the Russian astronomers in these studies, and the necessity of international cooperation."

The XXth meeting of the IAU in Australia in 1973 made the venue for the IAU Symposium No. 59 on Stellar Instability and Evolution, at Mount Stromlo Obser vatory on August 16-18, a very appropriate one. Many of the current and former staff of Mount Stromlo Observatory (operated by the Australian National Univer sity) have specialized in the study of variable stars and it was with considerable pleasure that Mount Stromlo Observatory accepted the responsibility of hosting and making the local arrangements for IAU Symposium No. 59. The Scientific Organizing Committee was particularly active in formulating the program and comprised Drs N. Baker, P. Demarque, M. Feast, G. Herbig, I. Iben, P. Ledoux, J. Ostriker and E. Schatzman. The aim of the Committee was to integrate the review and contributed papers on the particular instability mechanisms involved, their observational manifestations and their relation to the internal structure of the star as inferred from its evolutionary history. The Local Organizing Committee consisted of Miss P. Petrie and A. W. Rodgers."

'Galactic Radio Astronomy' was chosen as the subject of this Symposium, which was held in conjunction with the IAU General Assembly that took place in Sydney in August 1973, largely because it is a very suitable Southern Hemisphere topic. This results in part from the advantages of a southern location in studying the Galaxy and in part from the long association of Australia with radio astronomy. Following the General Assembly, the Symposium was held at the Surf air Inter national Hotel in Maroochydore, Queensland, from 3 to 7 September, 1973. The conference participants were effectively isolated from the rest of the world during the Symposium, and the excellent spring weather and geographical situation led to the development of an unusually good rapport. The Symposium was sponsored by Commissions 40, 33, and 34. The Organizing Committee was composed of A. H. Barrett (chairman), J. E. Baldwin, D. S. Heeschen, F. J. Kerr, J. Lequeux, S. W. McCuskey, P. G. Mezger, B. Y. Mills, Yu. N. Parijskij, B. J. Robinson, H. van der Laan, and H. F. Weaver. The Local Committee, consisting ofB. J. Robinson, N. G. Seddon, and P. J. Kelly, looked after the arrangements in very fine style. The Symposium was supported financially by the IAU, the Australian Academy o Science, the CSIRO Division of Radiophysics, Union Carbide Australia Limited, and the Science Foundation for Physics within the University of Sydney."

Proceedings of IAU Symposium No. 58 held in Canberra, Australia, August 12-15, 1973

The idea of the symposium came during the XVllth General Assembly of the IAU at Montreal. The Working Group on Be stars adopted both the proposal of holding a meeting, and of having it at the Universitats- sternwarte Munich. The meeting was organized under the auspices of IAU Comm. 29 (Stel- lar Spectra) and the sponsorship of Comm. 45 (Stellar Classification). The Scientific Organizing Committee was composed of Mercedes Jaschek (chairman), W. Bonsack, C. de Loore, A. Feinstein, H. G. Groth, P. Harmanec, L. Houziaux, A. M. Hubert-De1p1ace, L. S. Luud, A. Slettebak and A. Underhill. The members of this committee are to be thanked for their devotion to the organization of what turned out to be a very successful meeting. The program was organized on an observational approach, comprising sessions on photometry, polarization, spectroscopy, infrared observations, rotation and binarity, X-ray observations, UV observations and mass loss, and atmospheric models. Each session started with an invited summary paper, followed by a number of contributions. The different sessions were chaired by A. Feinstein, R. Sta1io, C. de Loore, Ch. Fehrenbach, J. P. Swings, C. Jaschek, A. Sapar, G. T. Traving, M. de Groot and H. G. Groth. Upon request of the Working Group., a special session was devoted to bibliographic problems and observing campaigns. The Dean of the Faculty for Physics 0.GBP the Ludwig-Maximilians-, Universitat welcomed the participants at the beginning of the Symposium. The meeting was closed by a summary talk, delivered by ~. P. Snow.

In connection with arranging IAU Symposium No. 50 on 'Spectral Classification and Multicolour Photometry', sponsored by Commissions 45 and 25, it was decided to exclude all calibration problems. Instead it was agreed that we should attempt to arrange a separate symposium, dealing with the fundamental problems of the cali bration of absolute magnitudes and temperatures of stars. The Executive Committee of the IAU accepted our proposal, and IAU Symposium No. 54 was held in Geneva on September 12-15, 1972, sponsored by thefollowing IAU Commissions: 24, 25, 29, 33, 35, 37,44 and 45. It was attended by about 90 scientists representing 16 countries. The Symposium was divided into eight sessions. Each session started with a review paper by an invited speaker; this was followed by a general discussion including a few contributed papers. The contents of the present volume follow closely the programmes of the individual sessions of the Symposium. Most of the recorded discussions have been kept, and only in a few cases have the order of questions and comments been altered so as to obtain more homogeneity in the presentation."

The proposal to organize a Symposium on circumstellar matter and extended atmo spheres in binary systems was first made by the Dominion Astrophysical Observatory to the Executive Committee of the International Astronomical Union in the summer of 1969. It received the support of the presidents of Commissions 29 (Stellar Spectra), 30 (Radial Velocities), 36 (Stellar Atmospheres), and 42 (Photometric Double Stars). Approval in principle was given by the Executive Committee almost immediately, and the Committee further suggested that the Symposium be officially designated the Struve Memorial Symposium. Final approval was given at the time of the 1970 General Assembly of the Union. when the dates of the Symposium were set for August or September, 1972. The Organizing Committee set up consisted of K. O. Wright (Chairman), A. H. Batten, K. -H. B6hm, A. A. Boyarchuk, G. Larsson-Leander, and M. Plavec. In addition, J. Sahade and F. B. Wood acted as advisory members. Local organization was entrusted to a committee consisting of A. H. Batten, E. K. Lee, and C. D. Scarfe. The final dates selected were September 6-12, 1972, and the Sym posium was held at the Island Hall Hotel, Parksville, B. C., on Vancouver Island some 90 miles from Victoria. The Organizing Committee attempted to arrange a Symposium of the type in which no contributed papers would be presented and discussion would range as widely as possible over the field covered by the six invited review papers."

We have in this volume, compiled a connected account of the proceedings of the Symposium on Wolf-Rayet and High-Temperature Stars held at Buenos Aires. The Organizing Committee had assigned broad areas of topical interest to be reviewed by invited speakers. Each of these presentations was followed by lengthy discussions that were tape recorded and transcribed later. These discussions have been edited only to a limited extent. We have shortened them and rearranged them to bring about a greater coherence. We have, however, attempted to retain the tenor of the discussions, the flavour of impromptu remarks and the continuity of an argument. Much of the success of such a venture depends on the contributors to the discussions. To be able to make these thoughts available to a larger audience has been the task of those re sponsible for the elaborate tape recording of the proceedings. We thank those at the Instituto de Astronomia y Fisica del Espacio for the efficient way in which this re sponsibility has been discharged. Many at Buenos Aires and Kodaikanal have contrib uted efficient assistance to the preparation of this volume and we are deeply indebted for their help. In particular, two amongst these, Nora Martinez and A. M. Batcha have contributed overwhelmingly both to the organization of the symposium and the final preparation of the symposium volume. Financial support for this symposium came from the International Astronomical Union and the Argentine National Research Council."