Jan H. Dort's work Ad: r>iaan Blaauw Meritus Emeritus Harry van der Laan 21 Jan Hendrik Dort and Dutch astronomy H. G. van Bueren 31 Dort's scientific importance on a world-wide scale Bengt Stromgren 39 Gart and international co-operation in astronomy D. H. Sadler 45 Reminiscences of the early nineteen-twenties Peter Van de Kamp 51 The first five years of Jan Dort at Leiden, Bart J. Bok 1924-1929 55 Early galactic structure Per Olof Lindblad 59 Early galactic radio astronomy at Kootwijk C. A. Muller 65 W. N. Christiansen Dort and his large radiotelescope 71 Ten years of discovery with Dort's Synthesis Radio Telescope R. J. Allen and R. D. Ekers 79 Gort's work on comets Maarten Schmidt 111 The evolution of ideas on the Crab Nebula L. WoUjer 117 Gort's work reflected in current studies of galactic CO W. B. Burton 123 On high-energy astrophysics V. L. Ginzburg 129 Dort and extragalactic astronomy Margaret and Geoffrey Burbidge 141 Birthday wishes John A. and Janette Wheeler 151 The Earth and the Universe Abraham H. Oort 153 The challenge of Jan Dort J. H. Bannier 157 Jan Dort at the telescope Fjeda Walraven 161 Gart Westerhout Personal recollections 163 Style of research Henk van de Hulst 165 Manuscript Jan H.

Originally published in 1957, this book presents symposium number 4, organised by the International Astronomical Union, held on 25th-27th August 1955 at the Jodrell Bank Experimental Station of the University of Manchester. This volume contains all but two of the papers presented and one contribution, paper 16, has been added at the editor's request. Furthermore, 'many papers have been improved as a result of discussion at the symposium or by the inclusion of data not available in August 1955'. The papers are broad in scope and detailed; chapter titles include, 'Spectral line investigations', 'Galactic structure and statistical studies of point sources' and 'Meteors and planets'. Diagrams are included for reference throughout. This book will be of significant value to astronomy scholars as well as to anyone with an interest in physics, cosmology and the history of science.

IAU Symposium Number 52 on Interstellar Dust and Related Topics was held at Albany, N.Y., on the campus of the State University of New York at Albany from May 29 to June 2, 1972. The members of the Organizing Committee were: Dr A. D. Code, University of Wisconsin, Madison, Wis., U.S.A. Dr B. D. Donn, Goddard Space Flight Center, Greenbelt, Md., U.S.A. Dr A. Elvius, Stockholm Observatory, Saltsjobaden, Sweden. Dr T. Gehrels, Lunar and Planetary Laboratory, University of Arizona, Tucson, Ariz., U.S.A. Dr J. M. Greenberg (Chairman), State University of New York at Albany, Albany, N.Y., U.S.A. Dr H. C. van de Hulst, Sterrewacht, Leiden, Holland. Dr S. B. Pikel'ner, Sternberg Astronomical Institute, Moscow, U.S.S.R. Dr E. E. Salpeter, Cornell University, Ithaca, N.Y., U.S.A. Dr B. E. Turner, National Radio Astronomy Observatory, Charlottesville, Va., U.S.A. The suggestion was first made in 1971 that a symposium on interstellar grains would be timely. The response to the first preliminary announcement, which was sent out on November 29, 1971, was well beyond our expectations. The meeting was locally sponsored by the State University and by Dudley Observatory. The National Aeronautics and Space Administration and the National Science Foundation con tributed along with the IAU. There were 158 participants of whom 49 were from 15 countries outside the United States. A total of 92 papers were presented."

IAU Symposium Number 52 on Interstellar Dust and Related Topics was held at Albany, N.Y., on the campus of the State University of New York at Albany from May 29 to June 2, 1972. The members of the Organizing Committee were: Dr A. D. Code, University of Wisconsin, Madison, Wis., U.S.A. Dr B. D. Donn, Goddard Space Flight Center, Greenbelt, Md., U.S.A. Dr A. Elvius, Stockholm Observatory, Saltsjobaden, Sweden. Dr T. Gehrels, Lunar and Planetary Laboratory, University of Arizona, Tucson, Ariz., U.S.A. Dr J. M. Greenberg (Chairman), State University of New York at Albany, Albany, N.Y., U.S.A. Dr H. C. van de Hulst, Sterrewacht, Leiden, Holland. Dr S. B. Pikel'ner, Sternberg Astronomical Institute, Moscow, U.S.S.R. Dr E. E. Sal peter, Cornell University, Ithaca, N.Y., U.S.A. Dr B. E. Turner, National Radio Astronomy Observatory, Charlottesville, Va., U.S.A. The suggestion was first made in 1971 that a symposium on interstellar grains would be timely. The response to the first preliminary announcement, which was sent out on November 29, 1971, was well beyond our expectations. The meeting was locally sponsored by the State University and by Dudley Observatory. The National Aeronautics and Space Administration and the National Science Foundation con tributed along with the JAU. There were 158 participants of whom 49 were from 15 countries outside the United States. A total of 92 papers were presented.

Jan H. Dort's work Ad: r>iaan Blaauw Meritus Emeritus Harry van der Laan 21 Jan Hendrik Dort and Dutch astronomy H. G. van Bueren 31 Dort's scientific importance on a world-wide scale Bengt Stromgren 39 Gart and international co-operation in astronomy D. H. Sadler 45 Reminiscences of the early nineteen-twenties Peter Van de Kamp 51 The first five years of Jan Dort at Leiden, Bart J. Bok 1924-1929 55 Early galactic structure Per Olof Lindblad 59 Early galactic radio astronomy at Kootwijk C. A. Muller 65 W. N. Christiansen Dort and his large radiotelescope 71 Ten years of discovery with Dort's Synthesis Radio Telescope R. J. Allen and R. D. Ekers 79 Gort's work on comets Maarten Schmidt 111 The evolution of ideas on the Crab Nebula L. WoUjer 117 Gort's work reflected in current studies of galactic CO W. B. Burton 123 On high-energy astrophysics V. L. Ginzburg 129 Dort and extragalactic astronomy Margaret and Geoffrey Burbidge 141 Birthday wishes John A. and Janette Wheeler 151 The Earth and the Universe Abraham H. Oort 153 The challenge of Jan Dort J. H. Bannier 157 Jan Dort at the telescope Fjeda Walraven 161 Gart Westerhout Personal recollections 163 Style of research Henk van de Hulst 165 Manuscript Jan H.