During July 1991. a group of 99 physicists from 57 laboratories in 27 countries met in Erice for the 29th Course of the International School of Subnuclear Physics. The countries represented were: Algeria. Argentina. Austria. Brazil. Canada. China. France. Germany. Greece. India. Ireland. Israel. Italy. New Zealand. Norway. Pakistan. Poland. Portugal. Rumania. Spain. Sweden. Switzerland. Thailand. Turkey. The Union of Soviet Socialist Republics. the United Kingdom. and the United States of America. The School was sponsored by the European Physical Society (EPS). the Italian Ministry of Education (MPI). the Italian Ministry of University and Scientific Research. the Sicilian Regional Government (ERS). and the Weizmann Institute of Science. The opening lecture of the School was given by Professor Lev Okun. A few remarks are in order. In the pre-Gorbachev era. Professor Okun's case was the most difficult: in spite of many invitations he was not allowed to come and lecture at Erice. Nowadays the hard times have nearly been forgotten. It is with pleasure that I recall here a discussion I had with my friend Lev Okun in my house during one of his rare visits to CERN. The after-dinner topic was Galileo Galilei and his great discovery; i. e . • the equality between gravitational and inertial masses - a discovery that we are celebrating now. four hundred years later. Here is a synthesis of Professor Okun's position: given a massive particle. the only quantity we should consider when talking about masses.

In this book, the fundamentals of magnetism are treated, starting at an introductory level. The origin of magnetic moments, the response to an applied magnetic field, and the various interactions giving rise to different types of magnetic ordering in solids are presented and many examples are given. Crystalline-electric-field effects are treated at a level that is sufficient to provide the basic knowledge necessary in understanding the properties of materials in which these effects play a role. Itinerant-electron magnetism is presented on a similar basis. Particular attention has been given to magnetocrystalline magnetic anisotropy and the magnetocaloric effect. Also, the usual techniques for magnetic measurements are presented. About half of the book is devoted to magnetic materials and the properties that make them suitable for numerous applications. The state of the art is presented of permanent magnets, high-density recording materials, soft-magnetic materials, Invar alloys and magnetostrictive materials. Many references are given.