tricity give rise to a variety of novel and striking phenomena, among which are those already described. The powerful electrical oscillations in the system E′ C E being 235communicated to the round cause corresponding vibrations to be propagated to distant parts of the globe, whence they are reflected and by interference with the outgoing vibrations produce stationary waves the crests 240and hollows of which lie in parallel circles relatively to which the ground-plate E may be considered to be the pole. Stated otherwise, the terrestrial conductor is thrown into resonance with the oscillations impressed 245upon it just like a wire. More than this, a number of facts ascertained by me clearly show that the movement of electricity through it follows certain laws with nearly mathematical rigor. For the present it will be 250sufficient to state that the planet behaves like a perfectly smooth or polished conductor of in appreciable resistance with capacity and self induction uniformly distributed along the axis of symmetry of wave propagation and 255transmitting slow electrical oscillations with out sensible distortion and attenuation.
Besides the above three requirements seem to be essential to the establishment of the resonating condition.
260First. The earth’s diameter passing through the pole should be an odd multiple of the quarter wave length-that is, of the ratio between the velocity of light-and four times the frequency of the currents.
265Second. It is necessary to employ oscillations in which the rate of radiation of energy into space in the form of hertzian or electromagnetic waves is very small. To give an idea, I would say that the frequency should be 270smaller than twenty thousand per second, though shorter waves might be practicable. The lowest frequency would appear to be six per second, in which case there will be but one node, at or near the ground-plate, and, 275paradoxical as it may seem, the effect will increase with the distance and will be greatest in a region diametrically opposite the transmitter. With oscillations still slower the earth, strictly speaking, will not resonate, but simply act as 280a capacity, and the variation of potential will be more or less uniform over its entire surface.
Third. The most essential requirement is, however, that irrespective of frequency the wave or wave-train should continue for a 285certain interval of time, which I have estimated to be not less than one-twelfth or probably 0.08484 of a second and which is taken in passing to and returning from the region diametrically opposite the pole over the earth’s 290surface with a mean velocity of about four hundred and seventy-one thousand two hundred and forty kilometers per second.
The presence of the stationary waves may be detected in many ways. For instance, a 295circuit may be connected directly or inductively to the ground and to an elevated terminal and tuned to respond more effectively to the oscillations. Another way is to connect a tuned circuit to the ground at two points lying more or less in a meridian passing300 through the pole E′ or, generally stated, to any two points of a different potential.
In Fig. 2 I have shown a device for detecting the presence of the waves such as I have used in a novel method of magnifying feeble305 effects which I have described in my Patents Nos. 685,953 and 685,955. It consists of a cylinder D, of insulating material, which is moved at a uniform rate of speed by clock-work or other suitable motive power and is 310provided with two metal rings F F′, upon which bear brushes a and a′, connected, respectively, to the terminal plates P and P′. From the rings F F′ extend narrow metallic segments x and x′, which by the rotation of315 the cylinder D are brought alternately into contact with double brushes b and b′, carried by and in contact with conducting-holders h and h′, supported in metallic bearings G and G′, as shown. The latter are connected to320 the terminals T and T′ of a condenser H, and it should be understood that they are capable of angular displacement as ordinary brush supports. The object of using two brushes, as b and b′, in each of the holders h and h′ is325 to vary at will the duration of the electric contact of the plates P and P′ with the terminals T and T′, to which is connected a receiving circuit including a receiver R and a device d, performing the duty of closing the 330receiving circuit at predetermined intervals of time and discharging the stored energy through the receiver. In the present case this device consists of a cylinder made partly of conducting and partly of insulating material e and e′, 335respectively, which is rotated at the desired rate of speed by any suitable means. The conducting part is in good electrical connection with the shaft S and is provided with tapering segments f f′, upon which slides a brush340 k, supported on a conducting-rod l, capable of longitudinal adjustment in a metallic support m. Another brush, n, is arranged to bear upon the shaft S, and it will be seen that, whenever one of the segments f′ comes in contact345 with the brush the circuit including the receiver R is completed and the condenser discharged through the same. By an adjustment of the speed or rotation of the cylinder350 d and a displacement of the brush k along the cylinder the circuit may be made to open and close in as rapid succession and remain open or closed during such intervals of time as may be desired. The plates P and P′, through which the electrical energy is conveyed to the355 brushes a and a′, may be at a considerable distance from each other in the ground or one in the ground and the other in the air, preferably at some height. If but one plate is connected to earth and the other maintained at an360