However, this beautiful and close collaboration lasted only a few years. In 1883, Pierre and Jacques were obliged to separate; Jacques left for the University of Montpellier as Head Lecturer in Mineralogy (_Maître de Conferences_). Pierre was made Director of Laboratory Work in the School of Industrial Physics and Chemistry founded by the city of Paris at the suggestion of Friedel and of Schützenberger, who became its first director. Their remarkable researches with crystals won for the brothers in 1895--very late, it is true--the Planté prize. [Footnote 1: Pierre Curie did not leave a veritable diary but only a few pages as chance permitted, covering but a short period of his life.] [Footnote 2: The piezo-electric property of quartz has recently had an important application; it has been utilized by P. Langevin in the production of elastic waves of high frequency (beyond sound) sent out in water with the aim of detecting submarine obstacles. This same method can serve in a more general manner to explore ocean depths. We see, here, once again, how pure speculation can lead to discoveries that will be useful later in unforeseen directions.] CHAPTER III LIFE AS THE DIRECTOR OF LABORATORY WORK IN THE SCHOOL OF PHYSICS AND CHEMISTRY. GENERALIZATION OF THE PRINCIPLE OF SYMMETRY. INVESTIGATIONS OF MAGNETISM It was in the School of Physics, in the old buildings of the Collège Rollin, that Pierre Curie was destined to work, first as Director of Laboratory Work, then as Professor, for twenty-two years, a period covering practically the whole of his scientific life. His memory seemed to cling to these old buildings, now destroyed, in which he had passed all his days, returning only in the evening to his parents in the country. He counted himself fortunate since he enjoyed the favor of the Founder-Director Schützenberger, and the esteem and good will of his students, many of whom became his disciples and friends. In alluding to this experience, at the close of an address delivered at the Sorbonne near the end of his life, he said: "I desire to recall here that we have made all our investigations in the School of Physics and Chemistry of the city of Paris. In all creative scientific work the influence of the surroundings in which one works is of great importance, and a part of the result is due to that influence. For more than twenty years I have worked in the School of Physics and Chemistry. Schützenberger, the first director of the School, was an eminent scientist. I remember with gratitude that he procured for me opportunities for my own investigations when I was yet but an assistant. Later, he permitted Madame Curie to work beside me, an authorization which was at that time far from an ordinary innovation.