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.