THE events I want to talk about took place more than fifty years ago. They are centred during World War I and the years immediately following. The principal actors in those events are famous men; they were, at least to their contemporaries, among the great men of science. I am not in a position to judge whether those men will be treated with the same reverence today as they were during my years in Cambridge, in the early and in the middle 1930s. Still, I hope that none of us will feel inclined to be disrespectful of the men and events I shall recall. Let me begin, then, with a conversation that took place in the Senior Combination Room in Trinity College, after dinner in hall, during the Christmas recess of 1933. During the Christmas recess, very few people normally dine in the College. On this particular occasion there were only five of us: Lord Rutherford, Sir Arthur Eddington, Sir Maurice Amos (at one time, during the 1920s, the Chief Judicial Advisor to the Egyptian government), Dr Patrick Du Val (a distinguished geometer), and myself. After dinner, we all sat around a fire and everyone, except myself, was smoking long white clay pipes—a traditional English custom during Christmas. Rutherford was in great form and was naturally the centre of the conversation.