The preparation of his class lectures was for Pierre Curie a genuine care. The Chair was a new one, and carried no prescribed course of study. He divided his lectures, at first, between crystallography and electricity. Then, as he recognized more and more the utility of a serious theoretical course in electricity for future engineers, he devoted himself entirely to this subject, and succeeded in establishing a course (of about 120 lectures) that was the most complete and modern then to be had in Paris. This cost him a considerable effort, of which I was the daily witness; for he was always anxious to give a complete picture of the phenomena and of the evolution of theories, and of ideas. He was always anxious, too, that his mode of exposition should be clear and precise. He thought of publishing a treatise summing up this course, but unfortunately the many preoccupations of the following years prevented him from putting this plan into execution.
We lived a very single life, interested in common, as we were, in our laboratory experiments and in the preparation of lectures and examinations. During eleven years we were scarcely ever separated, which means that there are very few lines of existing correspondence between us, representing that period. We spent our rest days and our vacations walking or bicycling either in the country near Paris, or along the sea, or in the mountains. My husband was so engrossed in his researches, however, that it was very difficult for him to remain for any length of time in a place where he lacked facilities for work. After a few days he would say: "It seems to me a very long time since we have accomplished anything." And yet he liked the excursions which covered successive days, and enjoyed to the full our walks together, just as he had formerly enjoyed those with his brother. But his joy in seeing beautiful things never drew his thoughts away from the scientific questions that absorbed him. In these free times, we traversed the region of the Cevennes and of the Monts d'Auvergne, as well as the coast of France, and some of its great forests.
These days in the open, filled with beautiful sights, made a deep impression on us, and we loved to recall them. One of our radiant memories was of a sunny day, when after a long and wearying climb, we reached the fresh, green meadow of the Aubrac, in the pure air of the high plateaus. Another vivid memory was that of an evening, when, lingering until twilight in the gorge of the Truyère, we were enchanted to hear a popular air dying away in the distance, carried to us from a little boat that descended the stream. We had taken so little notice of the time that we did not regain our lodging before dawn. At one point we had an encounter with carts whose horses were frightened by our bicycles, and we were obliged to cut across ploughed fields. At length we regained our route on the high plateau, bathed in the unreal light of the moon. And cows that were passing the night in enclosures came gravely to contemplate us with their large, tranquil eyes.
The forest of Compiegne charmed us in the spring, with its mass of green foliage stretching far as the eye could see, and its periwinkles and anemones. On the border of the forest of Fontainebleau, the banks of the Loing, covered with water buttercups, were an object of delight for Pierre Curie. We loved the melancholy coasts of Brittany and the reaches of heather and gorse, stretching to the very points of Finistère, which seemed like claws or teeth burying themselves in the water which forever rages at them.
Later, when we had our baby with us, we passed our vacations in some one locality, without traveling about. We lived then as simply as possible in retired villages where we could scarcely be distinguished from the villagers themselves. I remember the stupefaction of an American journalist when he found us one day at Pouldu, at a moment when I was sitting on one of the stone steps of our house in the act of shaking the sand from my sandals. However, his embarrassment was short-lived and, adapting himself to the situation, he sat down beside me and began jotting down in his notebook my answers to his questions.
The most affectionate relations existed between my husband's parents and myself. We often went to Sceaux, where the room my husband used to have before our marriage was always reserved for us. I had also a very tender affection for Jacques Curie and his family (he was married and had two children); for Pierre's brother became mine, and has always remained so.
Our eldest daughter, Irene, was born in September, 1897, and only a few days afterwards my husband suffered a great loss in the death of his mother. Doctor Curie came to live with us in a house which had a garden and was situated on the old fortifications of Paris (108 Boulevard Kellermann) near the park of Montsouris. Pierre Curie lived in this house until the end of his life.
With the birth of our child, the difficulties of carrying on our work were augmented: for I had to give more time to the household. Very fortunately for us I could leave my little girl with her grandfather, who much enjoyed taking care of her. But we had to think also of increasing our resources to meet the needs of our larger family and to enable us to secure someone to help me in the house, a necessity from now on. However, our situation remained as it was during the following two years, which we consecrated to intensive laboratory research on radioactivity. It was, indeed, not relieved until 1900, to the detriment, it is true, of the amount of time we could give to our investigations.
All formal social obligations were excluded from our life. Pierre Curie had for such things an unconquerable repugnance. Neither in his earlier nor his later life would he pay visits or undertake to involve himself in relations without special interest. By nature grave and silent, he preferred to abandon himself to his own reflections, rather than to engage in an exchange of banal words. On the other hand, he valued greatly his boyhood friends, and those to whom he was bound by a common interest in science.
Among the latter, E. Gouy, professor of the faculty of sciences at Lyon, should be named. His friendly relations with Pierre Curie dated from the time when they were both preparators at the Sorbonne. They carried on regularly a scientific correspondence, and took great pleasure in seeing each other again during the various brief visits of E. Gouy to Paris, on which occasions they were inseparable. There existed also a friendship of long standing between my husband and Ch. Ed. Guillaume, now director of the International Bureau of Weights and Measures of Sèvres. They met at the Physics Society and occasionally on Sundays at Sèvres or Sceaux. Later a group of younger men formed themselves about Pierre Curie. They were investigators engaged, as he was, in physical and chemical research in the newest fields of these sciences. Among these men were André Debierne, my husband's intimate friend and collaborator in the work on radioactivity; George Sagnac, his collaborator in a study of the X-rays; Paul Langevin, who became a professor in the Collège de France; Jean Perrin, at present professor of physical chemistry in the Sorbonne; and Georges Urbain, student of the School of Physics and later professor in the Sorbonne. Often one or the other came to see us in our quiet house in the Boulevard Kellermann. Then we engaged in discussions of recent or future experiments, or of new ideas and theories, and never tired of rejoicing over the marvelous development of modern physics.