Reporter's Statement of the Case

95 C. Cls.

interconnected or braced by rigid structural members, the towers being of pyramidal form with the lower ends thereof insulated from the earth by insulators.

None of the patents refer to any particular form of ground to be used in connection with the antenna, this portion of the transmitting system obviously being left to the choice of those skilled in the art.

Figures 9 and 10 of the patent to Jenner are reproduced herewith. This tower as shown is of rectangular crosssection at the base and is provided with insulators 44 in each of the four legs and a central or strain insulator 54 in the center of the tower. The particular type of pyramidal selfsupporting tower shown in these figures and disclosed in the Jenner patent is substantially the same as the antenna tower used in the Government structures.

22. U. S. Patent to Stone No. 767,974, issued August 16, 1904 (plaintiff's Exhibit 7-A), sets forth in the introductory portion of the specification that effective radiation of radio waves from an elevated conductor can be increased by "artificially increasing the natural electrical conductivity of the surface of the earth or other natural media in the immediate vicinity of the base of the transmitting-wire and maintaining said surface in a constantly-conducting state."

The specification contains the following disclosure with reference to accomplishing the desired effects:

For making the surface of the earth more highly conducting and maintaining it in a constantly-conducting state a multiplicity of substances may be used. In the drawing I have illustrated one embodiment of my invention in which metallic wire-netting of large mesh, known as "chicken-coop" netting, is placed in electrical contact with the earth surrounding the lower end of the elevated conductor and is connected to the lower end of said conductor. Such netting has been used successfully for the purpose herein specified. I have also used a layer of commercial calcium chlorid, although any other deliquescent salt which by virtue of its moisture-absorbing properties will maintain the surface of the earth in a constantly-moistened condition may be used, and a layer of such salt may with advantage be spread upon the earth within the area covered by the wire-netting. A solution of water and any conducting salt may be used.

Reporter's Statement of the Case

95 C. Cls.

The drawing of the patent, which is reproduced herewith, is illustrative of the means whereby the conductivity of the surface of the earth in the neighborhood of the base of the antenna is increased.

With reference to the size of the conducting surface or netting to be utilized the specification states as follows:

Although it is indicated by theory that any means employed to increase the natural electrical conductivity of the earth should extend from the base of the elevated conductor a distance equal to a quarter-wave length of the transmitted wave, it is to be distinctly understood that this length is merely the maximum length which may be advantageously employed, while excellent results

357

Reporter's Statement of the Case

may be obtained by using a much shorter length. In other words, the area of the netting or system of wires or other means specified herein may be much smaller than the area of a circle whose radius is equal to a quarter-wave length of the transmitted wave, although better results are obtained as this area is approximated.

23. The U. S. Patent to Fessenden 706,746, issued August 12, 1902 (defendant's Exhibit 57-A), Figs. 1, 2 and 4 of which are reproduced herewith, discloses a vertical antenna having an artificial ground composed of a highly conducting surface extending outwardly from the antenna and located at the base thereof.

Reporter's Statement of the Case

95 C. Cls.

As disclosed in the figures reproduced, the artificial ground consists of a plurality of radial wires laterally connected by other wires in the form of a spider web, the radial wires being grounded at their extremities. In connection with this disclosure the patentee states:

I have found that it is essential for the proper sending and receipt of these waves that the surface over which they are to travel should be highly conducting. more especially in the neighborhood of the point where the waves are generated. I have found that this highly conducting portion of the surface should preferably extend to at least a distance from the origin equal to a quarter wavelength of the wave in air and in the direction toward the station or stations to which it is desired to send the waves. Where the sending station is in a city or similar place where the waves may be cut off by high buildings or high trees, this highly conducting path should be extended still farther until it passes beyond the limits of the obstacle, and there the highly conducting portion, which may be in the form of a strip of metal or other conductor or of a number of wires, is connected to ground. This arrangement may be called a "wave-chute."

Figs. 1 and 2 disclose the arrangement of radio conductors in connection with the high buildings discussed, supra, by the patentee, and Fig. 4 discloses an artificial ground extending uniformly in every direction, Fig. 4 being referred to in the specification "as a plan view showing arrangement of station on rocky shore or other nonconducting ground."

The function of the ground system disclosed by the patent is stated in the specification as follows:

Another very important function of the construction here described is that it enables the capacity and selfinduction of the sending-station to be maintained constant, which is of fundamental importance in working tuned circuits. It frequently happens that stations are situated on rocky portions of coast where salt spray sometimes dashes up and renders portions of the groundsurface near the station conducting which were previously insulating, hence changing the capacity and inductance of the sending-conductor. If, however, the surface be covered by the network or strips heretofore described, the capacity will not be changeable, but constant, as the surface near the station is maintained in