I. Galactic Background Radiation.- A. The Beginning of Radio Astronomy.- 1. Directional Studies of Atmospherics at High Frequencies.- 2. Electrical Disturbances Apparently of Extraterrestrial Origin.- 3. A Note on the Source of Interstellar Interference.- B. First Maps of the Galaxy.- 4. Cosmic Static.- 5. Cosmic Static.- 6. Cosmic Static.- 7. Cosmic Static.- C. Free-Free Emission Theory.- 8. Interstellar Radiation from Free Electrons and Hydrogen Atoms.- D. Synchroton Radiation and Cosmic Rays.- 9. Cosmic Rays as the Source of General Galactic Radio Emission.- 10. Cosmic Rays as the Source of Galactic Radio Emission.- II. Techniques.- E. The Dicke Radiometer.- 11. The Measurement of Thermal Radiation at Microwave Frequencies.- F. The Phase-Switched Interferometer.- 12. A New Radio Interferometer and its Applica¬tion to the Observation of Weak Radio Stars.- III. The Solar System.- G. Early Solar Searches.- 13. On an Attempt to Detect Electrodynamic Solar Radiation and on the Change in Contact Resistance when Illuminating Two Conductors by Electric Radiation.- 14. A Search for Hertzian Waves Emanating from the Sun.- 15. On the Search for Hertzian Radiation Emanating from the Sun.- H. Detection of the Sun.- 16. Solar Radiations in the 4-6 Metre Radio Wave-Length Band.- 17. Microwave Radiation from the Sun (with Erratum).- I. First Solar Interferometry.- 18. Solar Radiation on 175 Mc/s.- 19. Solar Radiation at Radio Frequencies and its Relation to Sunspots.- J. The Hot Solar Corona.- 20. Temperature Radiation from the Quiet Sun in the Radio Spectrum.- 21. Observation of Million Degree Thermal Radiation from the Sun at a Wave-Length of 1.5 Metres.- K. Lunar Radiation.- 22. Microwave Radiation from the Sun and Moon.- IV. Discrete Sources.- L. Discovery and First OpticalIdentifications.- 23. Fluctuations in Cosmic Radiation at Radio-Frequencies.- 24. Variable Source of Radio-Frequency Radiation in the Constellation of Cygnus.- 25. A New Intense Source of Radio-Frequency Radiation in the Constellation of Cassiopeia.- 26. Positions of Three Discrete Sources of Galactic Radio-Frequency Radiation.- M. Synchroton Radiation.- 27. Cosmic Radiation and Radio Stars.- N. Optical Identification of Cas A and Cyg A.- 28. An Accurate Determination of the Positions of Four Radio Stars.- 29. Identification of the Radio Sources in Cassiopeia, Cygnus A, and Puppis A.- O. Source Structure.- 30. Apparent Angular Sizes of Discrete Radio Sources.- 31. Apparent Angular Sizes of Discrete Radio Sources.- 32. Apparent Angular Sizes of Discrete Radio Sources.- 33. Fine Structure of Extra-Terrestrial Radio Source Cygnus I.- V. Spectroscopy.- P. Prediction of the 21-cm Line.- 34. The Origin of Radio Waves from Space.- Q. Prediction of Molecular Line Emission.- 35. Monochromatic Radio Emission from the Galaxy and the Possibility of its Observation.- R. Discovery of the 21-cm Line.- 36. Radiation from Galactic Hydrogen at 1420 Mc/s.- 37. The Interstellar Hydrogen Line at 1420 Mc/s and an Estimate of Galactic Rotation (with a short note from J. L. Pawsey).- References.- Name index.