When the frequency and potential necessary to produce the flaming and streaming discharges is increased new phenomena result and a brush and spray discharge is obtained. With suitable electrodes comprising a large number of small points the emanations resemble jets from a gas-flame escaping under high pressure. According to Tesla “they not only resemble but they are veritable flames, for they are hot. Certainly they are not as hot as a flame of gas, but they would be so if the frequency and potential would be sufficiently high.”

If the frequency and potential is further increased, the discharge will pass through several inches of solid glass. Ordinarily glass is an insulator of electricity, and yet in this case the streams flow through it apparently with the greatest freedom. The flow of luminous energy has a tendency to stream out and to be dissipated to such an extent that when the brush is produced at the positive electrode no disruptive discharges will occur, even though the hand or any conducting object is held within the stream, and what is even more singular, the luminous stream is not at all easily deflected from its path by the approach of a conducting body.

Under these remarkable conditions the energy loses its property of producing sensation when it comes in contact with or passes through the human body, and a person may now be connected with the source of high-potential and high-frequency currents and be completely charged, though he will feel nothing; that he is a portion of an oscillator, however, can be readily determined, for if a vacuum tube is brought near any part of his body it will glow due to the electric waves emanating from him. To illustrate how absolutely devoid the sensory nerves are to these currents, a vacuum tube may be held in the mouth, and a current passed through the lamp lights it and then continues on its course, passing through the membranes of the mouth, which are perhaps the most sensitive of any in the body, yet no sensation whatever is experienced. A half-dozen incandescent lamps may be lighted with current passing through the body and no sensation is felt although instant death would result were the rate of oscillation reduced within certain limits.

The current issues at an enormous voltage from a large number of small points, so that it seems like jets of burning gas escaping at high pressure.

To show the impedance a copper bar of large diameter offers to a high-frequency current, an incandescent lamp is short-circuited across the former and the current is thus given the choice of two paths, an apparently easy one of small ohmic resistance and high impedance through the copper rod, or a seemingly more difficult one of large ohmic resistance and low impedance through the lamp. While an ordinary current would of course choose the former, the extraordinary current traverses the latter path.

The practical application of these discharges is found in radiotherapy. Their use is being extended more and more, and by many it is considered a rational method in therapeutic practice. Heat, light, and electricity when properly applied have accomplished surprising results. With the apparatus shown not only are all the various remedial manipulations of electricity available, but current is also supplied suitable for producing the X-rays, ultra-violet light, etc.

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* As of Nov. 1, 2000