To some, this may not seem a very important discovery, "from a practical standpoint"; and doubtless it is not, from the "practical standpoint" of some people, because it does not affect the amount of their worldly possessions, or their ease, comfort and pleasure. It was hailed with delight by scientific men, however; because not only did it support the electro-magnetic theory of light, but the course of Hertz's work had demonstrated the suspected fact that the "receiver" of electric waves must harmonize in its electric dimensions with the transmitter, in order that the greatest amount of electric energy may be developed in the receiver; and it had thus given assistance to investigations then in progress on what we now call "wireless telegraphy." Many investigators were now in the field, among whom was the humble author of these pages. Little real progress was made until, in 1891, when Branly announced his amazing discovery and utilized it in his amazing invention, called the "coherer." His discovery was that, if a tube containing metal filings be placed in the "field" of the spark of an electric machine, Leyden jar, or Rhumkorff coil, it (the filings) will become a conductor of electricity when hit by the electric waves; and that it will revert to its normal state as a non-conductor, if smartly tapped: the effect of the waves being to cause the separate particles to co-here and form a continuous metal conductor; while the effect of the tapping was to jar the particles apart. The first use of this coherer was in place of the ring that Hertz had used; but its value as an instrument of practical usefulness in achieving electric communication without wires was almost immediately perceived--and demonstrated. The career of the wireless telegraph since Branly's great discovery has been as rapid, widespread and important as any other new agency has ever enjoyed, and possibly more so. That wireless telegraphy was a distinct invention may perhaps be questioned. If it was, who was the inventor? It is true that an invention does not have to be associated with any one inventor in order to have the right to be characterized as an invention; but in the case of the wireless telegraph, it seems safe to say that, although some of the separate steps toward its achievement were inventions, the final step was merely the adding together of these separate steps in a way that was perfectly obvious, and that several men accomplished almost simultaneously. As soon as Branly produced his coherer, the problem was thereby automatically solved. Every experimenter realized that it was merely necessary to use Branly's coherer, in place of any receiver previously used, and to "tune" the transmitting and receiving circuits into harmony.