I AM surprised that Prof. Becquerel should have read into a passing reference to his distinguished father‘s work, in my review of Prof. Gamow‘s book, any suggestion that the discovery of radioactivity was in any way "fortuitous". No such suggestion was intended. I had always imagined that the historic photographic plate was enclosed in some sort of light-proof wrapping, and might be legitimately, if briefly, described as a "packet of photographic material".