Letter from Thomas Gold to Dr Robert M Walker, Director, Laboratory of Space Physics, Washington University, St Louis, Missouri Was very glad to see Walker's discovery of the track record recognized by the election to the National Academy. It was a very major and significant step for many purposes, and although Gold has differences with him over interpretations based on the technique, he has had no doubt concerning the importance of the technique and of Walker's share in its discovery. 26 April 1973