Letter from Thomas Gold, to Dr Zdenek Kopal, Boeing Scientific Research Laboratories, PO Box 3981, Seattle, Washington On the nature of the error in Kopal's paper relating to the solar flare outbursts. Simpson's quoted figure was likely conservative, but appropriate for smaller events. Recommends that if the error appears in the published version of Kopal's paper, the author should submit a correction. Gold is reluctant to do so on so trivial a point as a numerical slip. 10 September 1964