Messieurs, the Congress which is about to terminate to-morrow has been truly a very great event. It is the first time, I believe, that there has been seen assembled in one grand international reunion that which our great minister, Colbert, had in mind, and that which we have realized for the first time in our Institut de France,--the union of letters, science, and arts. That this union shall maintain itself in the future is the dearest wish of my heart. Science is a unit, even as the Universe. The aspects which it presents know neither boundaries of states nor the political divisions established between peoples. In all civilized countries they calculate with the same figures, they measure with the same instruments, they employ the same classifications, they study the same historic facts, economics, and morals. If there exists among the different nations some differences in methods, these difference are slight. They are a benefit at the same time as well as a necessity. For the doing of the immense amount of work of research imposed on that part of humanity which thinks, it is necessary that the subjects of study should not be identically the same, or better, if they are identical, that the difference between the points of view from which they are considered in the different countries contribute to our better knowledge of their nature, their results, and their applications. It is necessary then that each people preserve their distinctive genius, their particular methods which they use to develop the qualities they have inherited. In exactly the same way that it is important in an orchestra that each instrument play in the most perfect manner, and with the timbre which accords with its nature, the part which is given to it, so in science as in music, the harmony between the players is a necessary condition, which each one ought to exert himself to realize. Let us endeavor then in scientific research to execute in the most perfect manner that part of the task which fate has devolved upon us, but let us endeavor also to maintain that accord which is a necessary condition to the harmony which will alone be able in the future to assure the progress of humanity.