The speed of publication achieved by Becquerel was fortunate, in that at the same time Sylvanus Thompson in London was working with uranium nitrate. He found that when the uranium salt was exposed to sunlight while resting on a shielded photographic plate, film blackening occurred directly beneath the location of the uranium nitrate. The President of the Royal Society, replying to Thompson on February 29th 1896, suggested that he should publish his findings without delay, but Thompson had been pre-empted by Becquerel. It was by such a short margin of time that the new Système International radiation unit of activity, defined in the 1980s, is now a becquerel and not a thompson!