Even though he was very much absorbed in the preparation of his course, and often ill, my husband continued, nevertheless, to work in the laboratory, which was becoming better and better organized. He had a little more space now, and could receive a few students. In collaboration with A. Laborde, he carried on investigations in mineral waters and gases discharged from springs. This was the last work he published.
His intellectual faculties were at this time at their height. One could but admire the surety and rigor of his reasoning on the theories of physics, his clear comprehension of fundamental principles, and a certain profound sense of phenomena which he had by instinct, but which he perfected during the course of a life entirely consecrated to research and reflection. His skill in experiment, remarkable from the beginning, was increased by practice. He experienced the pleasure of an artist when he succeeded with a delicate installation. He enjoyed, too, devising and constructing new apparatus, and I used jokingly to tell him that he would not be happy unless he made at least an attempt of this kind once every six months. His natural curiosity and vivid imagination pushed him to undertakings in very varied directions; he could change the object of his research with surprising ease.
He was scrupulously careful of scientific probity and of complete accuracy in his publications. These are very perfect in form, and none the less so in those parts where he applies the critical spirit to himself, expressing his determination never to affirm anything that does not seem entirely clear. He expresses his thought on this point in the following words: "In the study of unknown phenomena, one can make very general hypotheses and then advance step by step with the help of experience. This method of progress is sure but necessarily slow. One can, on the contrary, make daring hypotheses in which he specifies the mechanism of phenomena. Such a method of procedure has the advantage of suggesting certain experiments, and, above all, of facilitating reasoning by rendering it less abstract through the employment of an image. But on the other hand, one cannot hope thus to conceive a complex theory in accord with experiment. The precise hypothesis almost certainly includes a portion of error along with a portion of truth. And this last portion, if it exists, forms only a part of a more general proposition to which it will be necessary in the end to return."
Moreover, even though he never hesitated to make hypotheses, he never permitted their premature publication. He could never accustom himself to a system of work which involved hasty publications, and was always happier in a domain in which but a few investigators were quietly working. The considerable vogue of radioactivity made him wish to abandon this field of research for a time, and to return to his interrupted studies of the physics of crystals. He dreamed also of making an examination of diverse theoretical questions.
He gave much thought to his teaching, which constantly improved, and which suggested to him ideas on the general orientation of studies and on methods of teaching, which he believed should be based on contact with experience and nature. He hoped to see his views adopted by the Association of Professors as soon as it was formed, and to obtain the declaration "that the teaching of the sciences must be the dominant teaching of both the boys' and girls' lycées." "But," he said, "such a notion would have little chance of success."
But this last period of his life, so fecund, was, alas, soon to end. His admirable scientific career was to be suddenly broken at the very moment when he could hope that the years of work to come would be less hard than those which had preceded.
In , quite ill and tired, he went with me and the children to spend Easter in the Chevreuse Valley. Those were two sweet days under a mild sun, and Pierre Curie felt the weight of weariness lighten in a healing repose near to those who were dear to him. He amused himself in the meadows with his little girls, and talked with me of their present and their future.
He returned to Paris for a reunion and dinner of the Physics Society. There he sat beside Henri Poincaré and had a long conversation with him on methods of teaching. As we were returning on foot to our house, he continued to develop his ideas on the culture that he dreamed of, happy in the consciousness that I shared his views.
The following day, the th of April, , he attended a reunion of the Association of Professors of the Faculties of the Sciences, where he talked with them very cordially about the aims which the Association might adopt. As he went out from this reunion and was crossing the rue Dauphine, he was struck by a truck coming from the Pont Neuf, and fell under its wheels. A concussion of the brain brought instantaneous death. So perished the hope founded on the wonderful being who thus ceased to be. In the study room to which he was never to return, the water buttercups he had brought from the country were still fresh.
