As distinguished from this system, however, modern wireless telegraphy--so called--has its basis in the utilization of electric or ether waves in free space, such waves being set up by electric oscillations, or surgings, of comparatively high potential and high frequency, produced by the operation of suitable electrical apparatus. Broadly speaking, these oscillations arise from disruptive discharges of an induction coil, or other form of oscillator, across an air-gap, and their character is controlled by the manipulation of a special type of circuit-breaking key, by means of which long and short discharges are produced. The electric or etheric waves thereby set up are detected and received by another special form of apparatus more or less distant, without any intervening wires or conductors.

In November, 1875, Edison, while experimenting in his Newark laboratory, discovered a new manifestation of electricity through mysterious sparks which could be produced under conditions unknown up to that time. Recognizing at once the absolutely unique character of the phenomena, he continued his investigations enthusiastically over two mouths, finally arriving at a correct conclusion as to the oscillatory nature of the hitherto unknown manifestations. Strange to say, however, the true import and practical applicability of these phenomena did not occur to his mind. Indeed, it was not until more than TWELVE YEARS AFTERWARD, in 1887, upon the publication of the notable work of Prof. H. Hertz proving the existence of electric waves in free space, that Edison realized the fact that the fundamental principle of aerial telegraphy had been within his grasp in the winter of 1875; for although the work of Hertz was more profound and mathematical than that of Edison, the principle involved and the phenomena observed were practically identical--in fact, it may be remarked that some of the methods and experimental apparatus were quite similar, especially the "dark box" with micrometer adjustment, used by both in observing the spark.[25]