The authors would like to thank the Chatterton Astronomy Department of Sydney University for collaborating in this programme. The observations were carried out by B. L. Morgan;
R;
J;
Scaddan;
H. A. Vine (Imperial College) and R. Hanbury Brown;
Davis;
W. J. Tango (Sydney University). The authors would also like to thank the SRC for financial support and the Director and staff of the Anglo-Australian Observatory for their cheerful and invaluable assistance;