Tesla and Wireless Telegraphy

Through the New York Sun, Tesla announced last week that
he is about to begin the construction of a plant for telegraphing without wires across the Atlantic Ocean, and that he estimated the work of preparation will consume eight months, adding, however, "but I am prepared to encounter some delays and drawbacks which always turn up somehow." From a statement in the same journal, it appears that the system to be employed was the subject of a patent issued to Tesla in May of last year. In looking over our files we find that two patents on "apparatus for transmission of energy" were issued to Tesla last spring, one dated March 20, and the other May 15; the latter is the one referred to by the Sun. We reproduce the following analyses of the patents from our issues of March 31 and May 26, 1900, respectively:

The patent dated March 20 (application filed Sept. 2, 1897), relates to the production at one point of an electrical pressure of such character and magnitude as to cause thereby a current to traverse elevated strata of the air between the point of generation and a distant point at which the energy is to be received and utilized. As illustrated, the apparatus consists of a generator supplying current to the primary of a transformer; the secondary consists of a coil of many turns and is connected at one side to the earth and at the other side to a terminal of large surface, maintained at a high elevation by such means as a balloon. The receiver duplicates this apparatus, except that instead of a generator being in one circuit of the transformer, receiving devices such as lamps and motors take its place.

The transformer consists of a coil of very large diameter wound in spiral form, either with or without a magnetic core. The inventor claims that this furnishes a practical method or system of transmission of energy through natural media without the use of wires.

The patent of May 15 (application filed Feb: 19, 1900), is on "apparatus for transmission of electrical energy." Referring to the accompanying illustration, which is a duplicate of that appearing in the patent of March 20, DD' are terminals of large surface maintained by such means as a balloon at a high elevation, the elevation depending upon the amount and quality of the work to be performed, the condition of the atmosphere, and also by the character of the surrounding country. The aerial conductors to these terminals are connected to the secondary of a spiral coil, the other end of the coil being connected to earth.

It is stated that the length of the thin wire in each of these coils should be approximately one-quarter of the wave length of the electric disturbance in the circuit, this estimate being based on the velocity of the propagation of the disturbance through the coil itself and the circuit with which it is to be used. For example, if the rate at which the current traverses the circuit including the coil be 185,000 miles per second, then the frequency of 925 miles per second would maintain 925 "stationary moves" in a circuit of 185 miles long, and each wave would be 200 miles in length. For such a low frequency, a secondary 50 miles in length would be used.

As will be noted from the illustration, the primary of the transmitting coil is supplied with a current by a dynamo, and the large coil of the receiver is connected with a circuit including lamps and motors. It is stated that the phenomenon involved in the apparatus is one of true conduction, and not to be confounded with the phenomena of electrical radiation which have heretofore been observed, and which from the very nature and mode of propagation will render practically impossible the transmission of any appreciable amount of energy to such distances as are of practical importance. The specification states that if the potential is sufficiently high and the ter- minals of the coil be maintained at the proper elevation where the atmosphere is rarefied, the stratum of air will serve as a conducting medium for the current produced, and the latter will be transmitted through the air "with, it may be, even less resistance than through an ordinary conductor."