This paper reports briefly on the provisional results of the 21-cm galactic work at the Radiophysics Laboratory, Sydney. Observations were made with a 36-ft, transit-type radio-telescope whose beam width at half-power is 1°.5 and a 4-channel receiver whose band width, 40 kcps, is equivalent to 8 km/sec.

The large scale structure of the galaxy has been studied by Kerr, Hindman, and Carpenter. They derive a general picture of the spiral structure in the southern hemisphere extending the Leiden results (see Fig. 1) and, in addition, a “relief map” of the galaxy showing the location of the densest parts of the hydrogen layer with respect to a central plane (see Fig. 2). Analysis of the spiral structure is for the present limited to regions beyond 3 kpc from the center. The Sydney and Leiden data agree well where they overlap, but location of spiral arms is sensitive to the choice of rotational model. Four or five spiral arms, or sections of arms, are indicated in the longitude interval l= 170° to l= 320°. The arms are clearly trailing in the rotation.