IN an earlier communication1 we reported a relatively heavy deposition of caesium-137 at Bergen, Norway, during the period September–October 1957. We suggested that this might have been due chiefly to the Windscale accident, meaning that about 5 mc./km2 of the measured 7.4 could not easily be accounted for by nuclear weapons tests, as the deposition in neighbouring periods was about 2 mc./km2 or less.