The study of continuous spectrum cosmic radio waves in the Radiophysics Laboratory is based mainly on two large ‘Mills Crosses’: one on 85 Mc./s. which has been in use for a year, and another on 20 Mc./s. which is under construction. The principle of this instrument has been described by Mills and Little (1953) . It utilizes two long thin arrays arranged in the form of a cross and gives an effective ‘pencil-beam’ response which records both the background and discrete sources simultaneously. Essential data relating to these Crosses are given in Table 1.