THE Gold Medal of the Royal Astronomical Society has been awarded to Dr. Edwin Hubble, Mount Wilson Observatory, California. Edwin Hubble joined the staff of the Mount Wilson Observatory in 1919. His first work was an investigation of the spectra and luminosity distributions of galactic nebulæ, and he established the now accepted connexion between the light from such nebulæ and the spectra of the stars involved. He proceeded to a general classification of what are now known as extra-galactic nebulæ, and then turned to intensive studies of M31 and M33, which considerably extended the list of novæ observed in them, and he identified Cepheid variables of galactic type as occurring in them. By means of the period-magnitude law for Cepheids he evaluated the distances of these nebulæ, which led in turn to estimates of their dimensions and masses and definitely established not only their extra-galactic nature but also their general similarity to our own galaxy. From this fundamental work followed the recognition of the nebulæ in general as extra-galactic but comparable with our own galaxy in structure. The 'island universe' controversy was thus settled.