He once told me something which proved that even at this time he was not content solely to follow a fixed program of studies, but that he had already begun to launch out into personal investigation. Strongly attracted by the theory of determinants, which he had just mastered, he undertook to realize an analogous conception, but in three dimensions, and endeavored to discover the properties and uses of these "cubical determinants." Needless to say that at his age, and with the knowledge then at his disposal, such an enterprise was beyond his powers. The attempt, however, was none the less indicative of his awakening inventive spirit. Several years later, when preoccupied with reflections upon symmetry, he asked himself the question: "Could not one find a general method for the solution of any equation whatever? Everything is a question of symmetry." He did not then know of Galois' theory of groups which had made it possible to attack this problem. But he was happy later to learn its results in the geometric applications to the case of equations of the 5th degree. Thanks to his rapid progress in mathematics and physics, Pierre Curie was made a bachelor of science at the age of sixteen years. With this he passed his most difficult stage of formal education. The only thing with which he had to concern himself in the future was the acquisition of knowledge through his personal and independent effort in a field of science freely chosen. CHAPTER II DREAMS OF YOUTH. FIRST SCIENTIFIC WORK. DISCOVERY OF PIEZO-ELECTRICITY Pierre Curie was still very young when he began his higher studies in preparation for the licentiate in physics. He followed the lectures and laboratory work at the Sorbonne and had, besides, access to the laboratory of Professor Leroux in the School of Pharmacy, where he assisted in the preparation of the physics courses. At the same time he became further acquainted with laboratory methods by working with his brother Jacques, who was then preparator of chemistry courses under Riche and Jungfleisch. Pierre received his licentiate in physical sciences at the age of eighteen. During his studies he had attracted the attention of Desains, director of the University laboratory, and of Mouton, assistant director of the same laboratory. Thanks to their appreciation he was appointed, when only nineteen years old, preparator for Desains and placed in charge of the students' laboratory work in physics. He held this position five years, and it was during this time that he began his experimental research.