When Madame Curie was asked on one occasion to what she attributed her success, she replied, without hesitation: "To my excellent training: first, under my father, who taught me to wonder and to test; second, under my husband, who understood and encouraged me; and third, under my children, who question me!" [Illustration: Madame and Dr. Curie and their little daughter Irene] It is the day of one of Madame Curie's lectures. The dignified halls of the university are a-flutter with many visitors from the world of wealth and fashion. There, too, are distinguished scientists from abroad, among whom are Lord Kelvin, Sir Oliver Lodge, and Sir William Ramsay. The President of France and his wife enter with royal guests, Don Carlos and Queen Amélie of Portugal, and the Shah of Persia. The plodding students and the sober men of learning, ranged about the hall, blink at the brilliant company like owls suddenly brought into the sunlight. At a given moment the hum of conversation dies away and the assemblage rises to its feet as a little black-robed figure steps in and stands before them on the platform. There is an instant's stillness,--a hush of indrawn breath you can almost hear,--and then the audience gives expression to its enthusiasm in a sudden roar of applause. The little woman lifts up her hand pleadingly. All is still again and she begins to speak. She is slight, almost pathetically frail, this queen of science. You feel as if all her life had gone into her work. Her face is pale, and her hair is only a shadow above her serious brow. But the deep-set eyes glow, and the quiet voice somehow holds the attention of those least concerned with the problems of advanced physics. Bank and wealth mean nothing to this little black-robed professor. It is said that when she was requested by the president to give a special demonstration of radium and its marvels before the Shah of Persia, she amazed his Serene Highness by showing much more concern for her tiny tube of white powder than for his distinguished favor. When the royal guest, who had never felt any particular need of exercising self-control, saw the uncanny light that was able to pass through plates of iron, he gave a startled exclamation and made a sudden movement that tipped over the scientist's material. Now it was the Lady Professor's turn to be alarmed. To pacify her, the Shah held out a costly ring from his royal finger, but this extraordinary woman with the pale face paid not the slightest attention; she could not be bribed to forget the peril of her precious radium. It is to be doubted if the eastern potentate had ever before been treated with such scant ceremony.