the insufficiencies of the others. We know very well that our science of today is a science of specialists. Not only is it impossible for anyone person to assimilate the totality of human knowledge, it is impossible even to know ones own discipline perfectly thoroughly. Each year the presses of science pro­ duce a frightening quantity of printed paper. Even in very limited fields, new journals are created every day, devoted to extremely specialized, often very narrowly defined subjects. It is indeed evident that in a field whose scope extends well beyond astronomical or astrophysical research, it is materially impossible to be informed of everything, even with the richest of libraries at hand.