THE death, the tragically early death, of Sir Ralph Fowler in Cambridge on July 28, 1944, at the age of fifty-five, leaves a gap in British and indeed in international mathematical physics which will be hard to bridge in the years that are to come. Whatever Fowler touched, he did well, superlatively well; he was a hard hitter, both at Work and games; and he had a quickness of apprehension, and power of plunging into a new subject, of getting abreast of all its details and more than holding his own with it in the presence of its acknowledged experts, at the shortest possible notice, that are exhibited in equal fashion perhaps only in the higher flights of advocacy. He was that rare combination, an accomplished pure mathematician with a sound physical insight. In fact, the only criticism I ever heard of his use of his powers was that he mistook physics as a field for the exercise of mathematical rigour. It was scarcely a fair criticism; only the gruelling training he received in pure mathematics at Cambridge, and the use that he put it to in his early pamphlet on the differential geometry of plane curves, could have given him the experience which was afterwards to mean that no non-rigorous deduction in mathematical physics proper ever escaped his trenchant and sometimes pungently expressed comments. He could make up his mind with lightning rapidity (he was a first-class bridge-player) and his conclusions were always strongly based on common sense, but his mathematical powers ensured that his strokes were savoured with something subtler than mere common sense.