This second title in the series published for the Space Telescope Science Institute researches the current models of quasar absorption and the systems of absorption lines in the spectra of quasars. Experts in this field discuss the nature of the absorbing process in the vicinity of quasars, the "Lyman-alpha forest", metal-line systems, and quasars as probes of high redshift galaxies. The Hubble Space Telescope will be a valuable tool for learning more about the physics and astronomy of quasars.

The controversial question of whether the majority of the narrow absorption lines observed in QSO spectra represent cosmological intervening systems or ejecta from the QSO themselves is settled. QSO absorption line spectroscopy, initially a mere technique, has matured into an essential extragalactic research tool for understanding the content of the Universe at redshifts between 0 and 4, and beyond. The only previous important meeting devoted to "QSO Absorption Lines" was held in May 1987 at the Space Telescope Science Institute in Baltimore, Maryland, U.S.A. Since that time, nearly a decade ago, research has been ex tremely active in this now well-established field of astrophysics. Theoretical stud ies and simulations have taken advantage of the constant progress in computer technology, and during these last few years, the observational results have bene fited largely from the new facillities offered by the Hubble Space Telescope in the UV wavelength range and the Keck Telescope for high-resolution spectroscopy.

Review of recent research in the field of quasar absorption line systems.

This volume presents lectures of the XI Canary Islands Winter School of Astrophysics written by experts in the field.

The present volume, the fourth one in the "Space Sciences Series of ISSI" (Inter national Space Science Institute), contains the proceedings of a workshop on "Pri mordial Nuclei and Their Galactic Evolution", which was held at ISSI in Bern on 6-10 May 1997. This topic was chosen following some general enquiries with the scientific community concerning its desirability and timeliness. Five convenors, D. Duncan, C. Hogan, J. Linsky, N. Prantzos, and H. Reeves (chair) subsequently set up the workshop, nominated a list of invitees, structured the workshop into a series of introductory talks and into six topical working groups (early Universe extragalactic objects -low-Z stars - galactic disk and galactic evolution - solar nebula -local interstellar medium), and described the tasks of the working groups in a list of keywords. It is the main task of ISSI to bring together space scientists, ground-based observers, and theorists from different fields and to give them the opportunity to discuss and compare their results, thus contributing to the achievement of a deeper understanding, adding value to those results through multi-disciplinary research in an atmosphere of international co-operation. In that spirit the convenors selected participants working in fields ranging from Big Bang theory to observers oftoday's Solar System, thus spanning the widest possible range both in time and space.