Industrial science is very much impressed by new discoveries which, as Rowland expressed it, “deal with the foundation of the universe,” but which in spite of their revolutionary character are easily understood by the practical man. Electron Physics abounds in discoveries of that kind, and it seems that they have rushed upon us like a cloud-burst. Things have been done that formerly seemed impossible. Take, for an illustration, a thing which is so familiar to all, the complete transformation of wireless telegraphy into the new art which is called Radio. A vacuum-tube with a hot filament fills up with negative electrons, which are thrown off by the hot filament. The filament may be said to be radioactive. A current can be established by applying an electromotive force which drives these negative electrons from the space surrounding the hot filament to a positive electrode. Here we have a new type of Crookes’s tube, operated by a small electrical tension, and not by that of a powerful induction-coil, which is necessary when the negative electrode is cold. This current is called the thermionic current, and its value can be varied in any way we please by a second electrical force which acts through a third electrode, called the grid, placed in the path of the thermionic current. This is the so-called audion tube, invented by a Yale graduate, Doctor Lee De Forest. In the hands of the Western Electric Company and of the General Electric Company, this tube has transformed the whole radio art by its amplifying power. My old inventions of electrical tuning and rectification have been raised to unexpected powers by the action of these tubes, and the inventions of my former pupil and research associate, Major E. H. Armstrong, and of others, have given us the broadcasting art, which surpasses the wildest expectations of even the rosiest of optimists of a few years ago. Wherever Electron Physics has entered there have sprung up new crops of the rarest fruit, and it is no wonder that there are to-day so many workers in the newly discovered fertile fields of the electromagnetic theory. Attend any meeting of the American Physical Society and you will be convinced that the research in the university laboratories as well as in the research laboratories of our industries would satisfy even the highest expectations of the men who fifty years ago, under the leadership of Joseph Henry, started the movement in favor of higher scientific research. The university and the industrial laboratories are mindful of Rowland’s admonition: “In choosing subjects for our investigation, let us, if possible, work upon those subjects which will finally give us advanced knowledge of some great subject.” What subject can be greater than eternal truth, and that aim, according to my definition, is idealism in science.