We were already working with tritium in Los Alamos as far back as 1945. I remember the time when Dr. Oppenheimer, wartime scientific director of Los Alamos, went to a large safe and brought out a small vial of a clear liquid that looked like water. It was the first highly diluted minute sample of superheavy water, composed of tritium and oxygen, ever to exist in the world, or anywhere in the universe, for that matter. We both looked at it in silent, rapt admiration. Though we did not speak, each of us knew what the other was thinking. Here was something, our thoughts ran, that existed on earth in gaseous form some two billion years ago, long before there were any waters or any forms of life. Here was something with the power to return the earth to its lifeless state of two billion years ago. The question of what type of hydrogen is to be used in the H-bomb therefore hangs on the question of which one of the possible combinations will catch fire by the light of a match that is blown out after an interval of about a hundred billionths of a second. On the answer to this question will also depend the time it will take us to complete the H-bomb and its cost. To make a bomb of a thousand times the power of the A-bomb would require a 1,000 kilograms of deuterium at a cost of $4,500,000, or 171 kilograms of tritium and 114 kilograms of deuterium at a total cost of more than $166,000,000,000 at current prices, not counting the cost of the A-bomb trigger. Large-scale production of tritium, however, will most certainly reduce its cost enormously, possibly by a factor of ten thousand or more, while, as will be indicated later, the amount of tritium, if required, may turn out to be much smaller. [Illustration: MAP BY DANIEL BROWNSTEIN] We can thus see that if deuterium alone is found to be all that is required to set off an H-bomb it will be cheap and relatively easy to make in a short time—both for us and for Russia. Furthermore, such a deuterium bomb would be practically limitless in size. One of a million times the power of the Hiroshima bomb is possible, since deuterium can be extracted in limitless amounts from plain water. On the other hand, if sizable amounts of tritium are found necessary, the cost will be much higher and it will take a considerably longer time, since the production of tritium is very slow and costly. This, in turn, will place a definite limit on the power of the H-bomb, since, unlike deuterium, the amounts of tritium will necessarily always be limited. As will be shown later, we are at present in a much more advantageous position to produce tritium than is Russia, so that if tritium is found necessary, we have a head start on her in H-bomb development.