Ptolemy was the most important physical scientist of the Roman Empire, and for a millennium and a half his writings on astronomy, astrology, and geography were models for imitation, resources for new work, and targets of criticism. Ptolemy in Perspective traces reactions to Ptolemy from his own times to ours. The nine studies show the complex processes by which an ancient scientist and his work gained and subsequently lost an overreaching reputation and authority.

This volume is a collection of experimental and theoretical papers presented at the international "Topical Meeting on Optical Bistability," held at the University of Rochester, June 15-17, 1983, sponsored jointly by the Air Force Office of Scientific Re search; the Army Research Office; and the Optical Society of America. The Conference, which had 150 attendees, overlapped (on June 15) with the Fifth Rochester Conference on Coherence and Quantum Optics with two joint sessions. Some of the topics cover ed in this volume are also treated io the Proceedings of that Conference. Since the last international conference on Optical Bistability, held in Asheville, North Carolina, June 3-5, 1980, there have been new and important fundamental advances in the field. This is borne out in papers in this volume dealing with optical chaos and period doubling bifurcations leading to chaos as well as the report of results of an experiment using a very simple system exhibiting ab sorptive optical bistability in a ring cavity using optically pump ed sodium atoms, which was successfully analyzed quantitatively by a simple theory. Other advances discussed here include the ob servation of optical bistability due to the effect of radiation pressure on one mirror of a fabry-Perot cavity. and the prediction of mirrorless intrinsic opittal bistability due to the local field correction incorporated into the Maxwell-Bloch formulation. Advances in optical bistability in semiconductors relate closer to actual device applications."

What is unorthodox in this book? Much has happened in the last few years, especially in terms of the somewhat surpris ing rate at which the theories presented herein have been gaining increasing acceptance and support even by the most skeptical professionals. Nevertheless, the purpose of this up-dated Preface is not to tell the biographical and acceptance story behind this book, but to bring together some non-physical and non technical conclusions for those readers who find the physico-mathematical sections of this book too difficult to follow. A secondary purpose is to present here some newer conclu sions, especially in general philosophy and in aesthetics. Yet, the main physico philosophical conclusions presented in this book are not to be summarized here. For that purpose one must tum to the text itself. * * * The theories presented here have been developed in total isolation. They were never presented in "professional conferences," as most current writers do. Whether or not that was important remains to be seen. Hence, all I can state to critics and enthusiastic follow ers alike is the fact that I do not belong to any 'formal discipline', 'pressure group', or 'pro fessional organization'."

Optics is reborn. There is fresh new vitality in applying old techniques to new prob lems and fully exploring novel phenomena. Lasers, holography, stellar navigation, nonlinear phenomena, and remote sensing are subjects of the seventies, and their further development will increase our understanding of nature and the development of technology. This Series is devoted to provid ing ideas and data to nourish the growth of these scientific and engineering en deavors' for we feel strongly that science and engineering flourish best when they grow together. Some of the volumes in the Series will be devoted to the optical properties of materials, theories of the detailed mechanisms of absorption, reflection, and nonlinea r phenomena, and electro-optical coefficients. The understanding of such things leads to further engineering applications. Companions to such theoretical books will be compendia of property data; the triad is completed by monographs on the use of the materials in op tical and electro-optical systems. Laser materials, lasers, and laser sys tems form one of the groups which will comprise the full set of ready-reference material for the entire field. The Series will be intentionally international, including a fair sampling of Russian work. There are important benefits to be obtained in the alternate approaches often taken by our Soviet and other foreign colleagues (just as they can gain from studying ours)."

First published in 1982, this volume summarises the proceedings of a conference which took place at the University of Oxford in September 1981. Held under the auspices of the International Astronomical Union and the International Union for the History and Philosophy of Science, the meeting reviewed the progress in the archaeoastronomy of the New World. American archaeoastronomy is growing healthily. Researchers from different disciplines, showing an interest in Native American astronomy, have been collaborating since the early 1970s. Research paths opened by astronomers, archaeologists, historians, anthropologists and ethnologists are converging. In this volume a number of these paths are explored and reviewed. The contents include a survey of progress in understanding Maya astronomy; astronomical and calendric practices of the Hopi and the Incas; and case studies of Bonampak (Mexico), Chaco Canyon, and Casa Rinconada.

Because of recent progress in the development of quasistationary toroidal mag- netic confinement systems, especially tokamaks, these systems are at the center of research on controlled thermonuclear fusion. Tokamaks were proposed and first built at the Kurchatov Institute of Atomic Energy. In the 1960s the basic features of plasma behavior in toroidal magnetic confinement systems were investigated in ex- periments on the first tokamaks and the possibility of obtaining effective confine- ment in them was demonstrated. The successes of this first stage led to a rapid ex- pansion in tokamak research around the world. The development of a thermonu- clear power reactor based on the tokamak is now actively under way. During the earliest phase of research on tokamaks, it was already clear that the ohmic heating used in them was not sufficient to obtain the temperatures needed for initiation of a self-sustaining thermonuclear reaction. At the beginning of the 1970s, therefore, a search was begun for methods of heating which could supple- ment ohmic heating. The best of these auxiliary heating techniques are neutral beam injection, various methods based on the collisionless absorption of rf (radio fre- quency) waves, and adiabatic compression of the plasma by a rising magnetic field.

The General Assemblies of the International Astronomical Union are landmarks in the life of the world-wide astronomical community, as they review, at triennial intervals, the progress made in this scientific field, promulgate the most spect acular astronomical achievements, formulate scientific programmes for the years to come and, last but not least, deal with the administration and finances of the IAU. The Reports on Astronomy 1976, published as Transactions XVIA (in 3 volumes) before the XVlth General Assembly, are a synopsis of the work done in astronomy from 1973 to 1975. The volume "Highlights of Astronomy, as presented at the XVlth General As sembly of the IAU in Grenoble, 1976" includes some selected scientific topics, and will appear in the first half of 1977. Apart from the Invited Discourses and the Proceedings of the seven Joint Discussions, the Highlights volume No.4 con tairsthe proceedings of two Joint Commissions Meetings."

The last decades have marked the beginning of a new era in Celestial Mech- ics. The challenges came from several di?erent directions. The stability theory of nearly-integrable systems (a class of problems which includes many models of - lestial Mechanics) pro?ted from the breakthrough represented by the Kolmogorov- Arnold-Moser theory, which also provides tools for determining explicitly the - rameter values allowing for stability. A con?nement of the actions for exponential times was guaranteed by Nekhoroshev's theorem, which gives much information about the geography of the resonances. Performing ever-faster computer simu- tionsallowedustohavedeeperinsightsintomanyquestionsofDynamicalSystems, most notably chaos theory. In this context several techniques have been developed to distinguish between ordered and chaotic behaviors. Modern tools for computing spacecraft trajectories made possible the realization of many space missions, es- cially the interplanetary tours, which gave a new shape to the solar system with a lot of new satellites and small bodies. Finally, the improvement of observational techniques allowed us to make two revolutions in the sky: the solar system does not end with Pluto, but it extends to the Kuiper belt, and the solar system is not unique, but the universe has plenty of extrasolar planetary systems. Cookingalltheseingredientstogetherwiththeclassicaltheoriesdevelopedfrom the 17th to the 19th centuries, one obtains themodern Celestial Mechanics.

decision and investigative process of the scientist, they can also wri te the paragra}ils of scientific resul ts. Once a canputer research activity progresses from intuitive guesses to a systematic study, the canputer program can free the scientist to pursue new original ideas. '!his concept is illustrated in the ptper by Hut. Sussnan says "Knowledge" is knowing what not to canpute. His main message is that we must change from trying to maximize the efficiency of the canputer to maximizing the effectiveness of the scientist. The canputer is relatively cheap, it is the trained scientist who is most valuable. In the second keynote address, R. L. Duncombe (University of Texas) described the "Early Applications of Canputer Technology to Dynamical Astronany. " His talk traced the worldwide introduction of punched card equipnent and their applications through the use of the first electronic canputers. Sussman and Duncombe, therefore, provided a forecast and review of the use of computers in dynamical astronany. This proceedings is intended to provide a consolidated general view of the ptst, present, and future of the Applications of Canputer Technology to Dynamical Astronany. Of necessity this requires that the ptpers be rela ti vely short and provide references to the more canplete discussions. Thanks to the representa tion from so many different countries the proceedings give a picture of the activities worldwide. The Scientific Organizing Comnittee included K. B. IIlatnagar, V. A. Brtmberg, G. Contopoulos, A. Depri t , J. Henrard, J. Kovalevsky, Y.

Neutrinos play an intriguing role in modern physics linking central questions of particle physics, cosmology and astrophysics. The contributions in this book reflect the present status of neutrino physics with emphasis on non-accelerator or beyond-accelerator experiments. Since a nonvanishing neutrino mass would yield an important boundary condition for GUT, SUSY or Superstring models and since neutrinos are the best candidates for dark matter in the universe, the many efforts to look for a neutrino mass, ranging from neutrino oscillation experiments using reactors, accelerators or the sun as neutrino sources, to tritium decay experiments and the search for neutrinoless double beta decay, are described in some detail. One of the sections is devoted to neutrinos from collapsing stars, including the supernova SN 1987 A. Possibilities for detecting cosmological neutrinos are discussed and an outlook to future experiments is given.

TH. HENNING and B. STECKLUM University Observatory. Jena This workshop was organized by the University Observatory Jena and devoted to the physics and chemistry of dense regions of interstellar matter. It was especially dealing with the properties of interstellar dust grains and star formation in those regions. This field of research was opened in Jena already in the 1950s and an early fA U Colloquium on the topic of interstellar matter was held here in 1969. Since that time, the subject of interstellar matter has grown into a much more important part of astrophysics than it was in 1969. Now we are beginning to understand the process of star formation in a greater detail. The discovery of many interstellar molecules by radioastronomers opened the new field of interstellar chemistry. In addition, the application of the new techniques of infrared astronomy led to the discovery of several absorption bands, e. g. , the 3. 1 11m ice band, which pointed to the existence of grain mantles. More recently, the detection of infrared emission lines was the first hint to the existence of a new component of interstellar matter. All these things were discussed extensively during the workshop. The very successful IRAS mission, which was also a subject of this workshop, gave us many new insights and unexpected findings, e. g. , the detection of infrared cirrus clouds.

The second workshop on High Energy Astrophysics of the Ma..x-Planck-Society and the Academia Sinica was held at Ringberg Castle near Tegernsee during the week July 12-July 17, 1987. It is the purpose of these workshops to en courage the exchange of ideas between German and Chinese astrophysicists (scientists from other countries are also welcome, of course), and the pleas ant atmosphere and surroundings of Ringberg Castle certainly helped the development of relaxed and stimulating discussions. In addition, we seemed to have picked out the one week of perfect weather during a rainy summer. Thanks are due to Mr. Hormann and his staff for creating a perfect infra structure. The proceedings have required a considerable amount of editing, and I hope that all the papers are comprehensible. Thanks are due to Miss Petra Berkemeyer and Miss Hannelore Muller, who patiently retyped several manu scripts and helped with other editing jobs. I did not feel that a sharp refer eeing procedure should be done, although I do not agree with all the papers in this volume. The interested reader will find that this book gives a fair account of the present status of Chinese activities in the field of high energy astrophysics, i.e. in supernova physics, accretion onto compact objects, active galaxies, and cosmology."

The last two subjects mentioned in the title "Wavelets" are so well established that they do not need any explanations. The first is related to them, but a short introduction is appropriate since the concept of wavelets emerged fairly recently. Roughly speaking, a wavelet decomposition is an expansion of an arbitrary function into smooth localized contributions labeled by a scale and a position pa rameter. Many of the ideas and techniques related to such expansions have existed for a long time and are widely used in mathematical analysis, theoretical physics and engineering. However, the rate of progress increased significantly when it was realized that these ideas could give rise to straightforward calculational methods applicable to different fields. The interdisciplinary structure (R.c.P. "Ondelettes") of the C.N .R.S. and help from the Societe Nationale Elf-Aquitaine greatly fostered these developments. This conference was held at the Centre National de Rencontres Mathematiques (C.I.R.M) in Marseille from December 14 to 18, 1987 and brought together an interdisciplinary mix of participants. We hope that these proceedings will convey to the reader some of the excitement and flavor of the meeting.

When physicist Robert Goddard, whose career was inspired by H. G. Wells's War of the Worlds, published "A Method of Reaching Extreme Altitudes," the response was electric. Newspaper headlines across the country announced, "Modern Jules Verne Invents Rocket to Reach Moon," while people from around the world, including two World War I pilots, volunteered as pioneers in space exploration. Though premature (Goddard's rocket, alas, was only imagined), the episode demonstrated not only science's general popularity but also its intersection with interwar popular and commercial culture. In that intersection, the stories that inspired Goddard and others became a recognizable genre: science fiction. Astounding Wonder explores science fiction's emergence in the era's "pulps," colorful magazines that shouted from the newsstands, attracting an extraordinarily loyal and active audience.

Pulps invited readers not only to read science fiction but also to participate in it, joining writers and editors in celebrating a collective wonder for and investment in the potential of science. But in conjuring fantastic machines, travel across time and space, unexplored worlds, and alien foes, science fiction offered more than rousing adventure and romance. It also assuaged contemporary concerns about nation, gender, race, authority, ability, and progress—about the place of ordinary individuals within modern science and society—in the process freeing readers to debate scientific theories and implications separate from such concerns.

Readers similarly sought to establish their worth and place outside the pulps. Organizing clubs and conventions and producing their own magazines, some expanded science fiction's community and created a fan subculture separate from the professional pulp industry. Others formed societies to launch and experiment with rockets. From debating relativity and the use of slang in the future to printing purple fanzines and calculating the speed of spaceships, fans' enthusiastic industry revealed the tensions between popular science and modern science. Even as it inspired readers' imagination and activities, science fiction's participatory ethos sparked debates about amateurs and professionals that divided the worlds of science fiction in the 1930s and after.

This volume is based on the proceedings of the "NATO Advanced study Institute on Mineral Processing Design" held in Bursa-Turkey on August 24-31, 1984. The institute was organized by Professor B. Yarar of the Colorado School of Mines, Golden, Colorado, 80401, USA, Professor G. Ozbayoghu and Professor Z. M. Dogan of METU-Ankara, Turkey, who was the director. The purpose of the institute was to provide an international forum on the subject and update the information available. Participants were from Turkey, England, Greece, Spain, Portugal, Belgium, Canada, and the USA. Besides authors contributing to this volume, presentations were also made by Drs. Yarar, Raghavan, Schurger, and Mr. Kelland. Many assistants and colleagues helped. They are gratefully acknowledged. Acknowledgment is also owed to Drs. Ek, de Kuyper, and Tolun. Dr. Gfilhan Ozbayoglu, and Mr. S. Ozbayoglu were particularly helpful in the overall organization and hosting of many international guests. We owe them special thanks. NATO, Scientific Affairs Division, is gratefully acknowledged for the grant which made this activity possible. Z. M. Dogan B. Yarar 2 APPLIED MINERALOGY IN ORE DRESSING William Petruk CANMET, 555 Booth Street, Ottawa, Ontario, KIA OGI ABSTRACT Mineralogy applied to ore dressing is a reliable guide for designing and operating an efficient concentrator. A procedure for conductiqg mineralogical studies in conjunction with ore dressing was, therefore, developed. The procedure includes characterizing the ore and analysing the mill products.

This book contains the lectures presented at the Summer Advanced Study School, 'Magnetospheric Particles and Fields' which was held at Graz, Austria during the period August 4-15, 1975. One hundred and one persons from fifteen different countries attended the Schoo . The authors and publisher have made a special effort for rapid publication of an up-to date status of particles, fields, and processes in planetary magnetospheres. Special thanks are due to the lecturers for their diligent preparation and excellent presentations. The in dividuallectures and the published papers were deliberately limited; the authors' cooper ation in conforming to these specifications is greatly appreciated. Many thanks are due to Drs C. D. Anger, Gerhard Haerendel, George P. Haskell, Carl McIlwain, Vytenis Vasy liunas, Martin Walt, and James Warwick who served as session chairmen during the School and contributed greatly to its success by skillfully directing the discussion period in a stimulating manner after each lecture. Many persons contributed to the success of the School. Drs C. D. Anger, Carl-Gunne Falthammar, Gerhard Haerendel, George P. Haskell, Carl McIlwain, David Nunn, Willi Riedler, Finn Scentsraas, Vytenis M. Vasyliunas, Martin Walt, and James Warwick were especially helpful in preparing the technical program. Dr Willi Riedler assisted in ar ranging for the facilities in Graz. Drs Gerhard Kremser and Martin Friedrich were most helpful with many aspects of the local arrangements in Graz. The assistant editor, Mrs Diana R. McCormac, checked the manuscripts and proofs, and worked hard to achieve a uniform style in this book."

The Sixth Trieste Conference on Chemical Evolution for the first time has also been a Euroconference. This year we focused on "First Steps in the Origin of Life in the Universe". (Both this Centre and the ICGEB have been sponsors since we first started planning the series with Professors Abdus Salam and Cyril Ponnamperuma. ) The conference had the following 11 sponsors: The Abdus Salam International Centre for Theoretical Physics, The European Commission, The SETI Institute, Consiglio Nazionale delle Ricerche, Rome, Italy, The International Centre for Genetic Engineering and Biotechnology, Trieste, The European Space Agency (ESA), National Aeronautics and Space Administration (NASA) Universite Paris 12, The ICTP Public Information Office, La Fondazione Internazionale Trieste per il Progresso e la Liberta della Scienza, and II Laboratorio dell'Immaginario Scientifico. of our Over 90 participants allowed us to make a truly comprehensive review subject. In 82 presentations we had contributions from experts in questions related to the origin, evolution, distribution and destiny of life in the universe, topics that are known together as the science ofastrobiology. The publication ofthese proceedings was largely due to a generous grant form the Consiglio Nazionale delle Ricerche, Rome, Italy. The general topic of the conference concerned the origin, evolution, distribution and destiny of life in the Universe, a subject referred to as astrobiology and also as exobiology. In this report we prefer the synonym Astrobiology.

Modern observations, including recent ones with the Hubble Space Telescope, have revealed that the Universe is replete with plasma outflows from all kinds of objects, ranging from stars in all their variety to galaxies. In this masterly survey of plasma astrophysics, written by leading practitioners, the first 15 articles in Part I deal with the use of the MHD approach in several key problems of solar plasma, such as magnetoconvection and magnetic field generation, sunspots and coronal loops, magnetic nonequilibrium and coronal heating, coronal mass ejections, the acceleration of the solar wind, and stellar winds across the Main Sequence. The following 16 articles of Part II deal with the use of the same MHD approach in several central and puzzling aspects of more distant astrophysical plasmas, such as the dynamics of the interstellar medium, collimated outflows from young stellar objects and accretion disks, molecular outflows and jets associated with enigmatic binaries and symbiotic stars, relativistic flows associated with superluminal microquasars in our own galaxy, astrophysical jets from nearby galaxies, or remote active galactic nuclei and quasars, probably fuelled by supermassive black holes. The emphasis throughout is on the striking underlying similarities in the physics of all these problems. Audience: Indispensable for solar physicists and astrophysics alike. An ideal textbook for graduate students in physics and astrophysics.

Particle physics seems to be entering a new period of consoli- dation. In 1977 when the first summer institute on particles and fields was held at the Banff Center, the standard model of the electro-weak interaction was a promising model more or less con- firmed; today it seems quite well-confirmed. QCD was considered as probably the correct theory of strong interactions; today most theo- rists take it for granted. What seems to be lacking are computa- tional tools and strenuous experimental testing; the major ideas seem to exist. Thus, this is a particularly auspicious time for a review of the status of theoretical and experimental particle physics and field theory. The lectures collected in this volume were presented from August 16 to August 27, 1981 at the Banff Center in Banff, Canada. The unifying theme was gauge fields and the topics covered dealt with electro-weak interactions, Q.C.D., sub-quarks and unified theories. The format of the Institute was as follows: thirteen lecture series of two to four hours each given by S. Brodsky, D. Bryman, M. Chen, S. Coleman, M. Creutz, H. Harari, J. Iliopoulos, C.H. Llewellyn- Smith, P. Lepage, D. Perkins and L. Susskind. In addition there were nine seminars (one hour each) given by G. Bodwin, G. Bunce, M.

The Cargese Workshop Random Surfaces and Quantum Gravity was held from May 27 to June 2, 1990. Little was known about string theory in the non-perturbative regime before Oetober 1989 when non-perturbative equations for the string partition functions were found by using methods based on the random triangulations of surfaees. This set of methods pro vides a deseription of non-eritical string theory or equivalently of the coupling of matter fields to quantum gravity in two dimensions. The Cargese meeting was very successful in that it provided the first opportunity to gather most of the active workers in the field for a fuH week of lectures and extensive informal discussions about these exeiting new developments. The main results were reviewed, recent advances were explained, new results and conjectures (which appear for the first time in these proceedings) were presented and discussed. Among the most important topics discussed at the workshop were: The relation of KdV theory to loop equations and the Virasoro algebra, new results in Liouville field theory, effective (1 + 1) dimensional theory for 2 - D quantum gravity coupled to c = 1 matter and its fermionization, proposal for a new geometrical interpretation of the string equation and possible definition of quantum Riemann surfaces, discussion of the string equation for the multi-matrix models, links with topological field theories of gravity, issues in using target space supersymmetry to define good theories, definition of the partition function via analytic continuation, new models of random surfaces

Proceedings of the Workshop held at the University of Rome, March 24-28, 1980

In many areas of physics, such as astrophysics, solid-state physics, nuclear physics and particle physics, a major outstanding problem is a better understanding of corre lation phenomena. While in most cases the average properties of a system are rather well understood, the correlations and the resulting clustering are poorly understood. They are reflections of the force mediating the interaction among the constituents and play essential roles in determining the structure of a physical system. At the largest scales, in astrophysics, it has recently been realized that there are huge voids in space and almost all matter is concentrated on filaments, raising interesting questions concerning the origin of this clustering of matter. In nuclear physics corre lation phenomena are important in all its subfields. It has been realized that so-called fluctuations in the one-particle density, which are a manifestation of nucleon-nucleon correlations, are crucial. These are important for an understanding of heavy-ion reac tions. This is the subject of modern quantum transport theories. Correlations are also crucial in the description of the high momentum components as observed in quasi-elastic knock-out reactions."

This textbook provides an introduction to the fundamentals of space physics and astrophysics and covers the recent progress in various aspects of these fields. In the introductory Chapter 1, a brief historical account of space research is given, followed by short reviews of the space vehicles used and some aspects of the early years of space research. In Chapter 2, the reader is introduced to the discoveries of the radiation belts and the magnetosphere of the Earth. Chapter 3 begins with the phenomena of the quiet Sun, followed by processes in the active Sun (solar flares, radio bursts and X-ray, gamma-ray and neutron emissions). In Chapters 4 and 5, attention is paid to the physical features and properties of large bodies and aggregates in the matter of the solar system, emphasising discoveries obtained from spacecraft. In Chapter 6 solar energetic particles are presented, bringing out their dual role - as a sample of accelerated matter from the Sun and as a sensitive probe of the interplanetary fields in the heliosphere. Chapter 7 presents a discussion on galactic cosmic rays, explaining the basic features and main findings. Highlights of ultra-high-energy cosmic rays and possible origins are included. Chapter 8 presents exciting results of extreme UV, infra-red, X-rays and gamma-rays from space. These are followed by outlines of the new vistas of cosmological problems as revealed by the cosmic background measurements of X-rays, gamma-rays and microwaves. In Chapter 9, the reader is introduced to the physical and dynamical properties of the interstellar medium. This chapter concludes with the astrophysical aspects of the search for the origin of life. In the concluding Chapter 10 some general trends and future directions are briefly presented. The level of presentation is aimed at senior undergraduate students who are familiar with introductory physics. Graduate students will find more advanced topics discussed through their underlying features. Each chapter is followed by a number of problems; solving these will enable students to obtain a good grasp of the topics.

The European Workshop on White Dwarfs was initiated by Prof. V. Weidemann, with the first meeting held in Kiel (FRG) in 1974. Since then a similar workshop has been held almost every two years: Frascati (1976), Tel Aviv (1978), Paris (1981), Kiel (1984), Frascati (1986) and Toulouse (1990). Two major IAU colloquia have also been devoted to the study of white dwarfs (No. 53, Rochester NY, 1979; No. 114, Hanover, NH, 1988). Our most recent meeting, the 8th Workshop, marks a number of important advances in both observational and theoretical studies of white dwarfs. This coincides with a significant expansion in the size of the community active in the field, as was clear from an increase in the number of participants between this workshop (77) and that in Toulouse (46), just two years ago. Key parts of any workshop are the discussion sessions following the pa pers. However, these are difficult to record and, very often, the 'live' flavour of the debates is lost. During this workshop we carried out an experiment, recording the discussion sessions on video tape and then transcribing these later for the proceedings. Although the recordings were made in non-studio conditions with regard to lighting and noise, only a very small part was unin telligible. All participants were given an opportunity to check their questions and answers for scientific accuracy and to correct any errors arising in the transcription process."

This second volume of Reviews in Modern Astronomy continues the new series of publications of the Astronomische Gesellschaft (AG). In order to bring the scientific events of the meetings of the society to the attention of the worldwide astronomical community, it was decided to devote a new annual publication, Reviews in Modern Astronomy, exclusively to the invited reviews, the Karl Schwarzschild lectures, and the highlight contributions from leading scientists reporting on recent progress and scientific achievements at their institutes. Volume 2 comprises the contributions presented during the spring meet- ing of the AG at Friedrichshafen in April 1989, which was dedicated to the topic "Astrophysics with Modern Technology - Space-based and Ground-based Systems", as well as those delivered at the fall meeting at Graz, Austria in September 1989. The Karl Schwarzschild lectures constitute a special series by outstanding scientists honoured with the Karl Schwarzschild medal of the Astronomische Gesellschaft. Between 1959 and 1987 the following scientists presented Karl Schwarzschild lectures at meetings of the Astronomische Gesellschaft: Martin Schwarzschild (1959) George Field (1978) Charles Fehrenbach (1963) Ludwig Biermann (1980) Maarten Schmidt (1968) Bohdan Paczynski (1981) Bengt Stromgren (1969) Jean Delhaye (1982) Antony Hewish (1971) Donald Lynden-Bell (1983) Jan H. Oort (1972) Daniel M. Popper (1984) Corne lis de Jager (1974) Subrahmanyan Chandrasekhar (1986) Lyman Spitzer Jr.