this was one major aim of this Conference. Because of the long theoretical and observational association of the Manchester Group with this general area, Manchester seemed an appropriate venue for this Con­ ference. But in fact this long association and the actual year of the Conference are connected. In 1951 Franz Kahn joined the Astronomy Department at Manchester University and immediately the study of diffuse media, particularly the hydrody­ namic aspects, commenced and has flourished ever since. Franz became Head of the Astronomy Department in 1981 following the retirement of Professor Z. Kopal, who founded the Department and was instrumental in attracting Franz to it. In 1993, Franz retired from this position and a most serendipidous coincidence was his election to the Royal Society announced shortly before the Conference.