Frontispiece

Presented is an image of contours of radio emission from the Great Nebula in Andromeda (M31) measured with The Ohio State University 260-foot radio telescope at 1415 Mc. The radio contours are superimposed on a Perkins Observatory photograph. This galaxy is at a distance of some two million light years and is believed to be quite similar to our own galaxy. The contour interval is 0.05° Kelvin of antenna temperature. The cross indicates the optical center and the small white circle the approximate radio center (Nature, vol. 202, p. 1202; 1964). The figure is about 3.5° wide by 4° high; the antenna beam size is shown at the top. This radio-optical presentation exemplifies the growing trend of combining radio and optical results in astronomical research.