Chapter XXX - The Martin Book
Alternate Current Electrostatic Induction Apparatus
About a year and a half ago while engaged in the study of alternate currents of short period, it occurred to me that such currents could be obtained by rotating charged surfaces in close proximity to conductors. Accordingly I devised various forms of experimental apparatus of which two are illustrated in the accompanying engravings.
In the apparatus shown in Fig. 208, A is a ring of dry shellacked hard wood provided on its inside with two sets of tin-foil coatings, a and b, all the a coatings and all the b coatings being connected together, respectively, but independent from each other. These two sets of coatings are connected to two terminals, T. For the sake of clearness only a few coatings are shown. Inside of the ring A, and in close proximity to it there is arranged to rotate a cylinder B, likewise of dry, shellacked hard wood, and provided with two similar sets of coatings, a1 and b1, all the coatings a1 being connected to one ring and all the others, b1, to another marked + and −. These two sets, a1 and b1 are charged to a high potential by a Holtz or Wimshurst machine, and may be connected to a jar of some capacity. The inside of ring A is coated with mica in order to increase the induction and also to allow higher potentials to be used.
When the cylinder B with the charged coatings is rotated, a circuit connected to the terminals T is traversed by alternating currents. Another form of apparatus is illustrated in Fig. 209. In this apparatus the two sets of tin-foil coatings are glued on a plate of ebonite, and a similar plate which is rotated, and the coatings of which are charged as in Fig. 208, is provided.
The output of such an apparatus is very small, but some of the effects peculiar to alternating currents of short periods may be observed. The effects, however, cannot be compared with those obtainable with an induction coil which is operated by an alternate current machine of high frequency, some of which were described by me a short while ago.
X and Y are the field and armature, respectively, for an early high-frequency alternator that was displayed in two separate pieces at the 1893 World's Fair.
[Fig. 10] shows a type of small alternator, one of two forms which I will show you, that from the constructive point of view, is rather poor. I will admit that. But, it was convenient for me to construct it that way. You see, the magnetic circuit is constituted by the laminated core here, [and] there is an exciting coil. In this picture you will also note the field wires, and the rotor is indicated. With this machine I could get 200,000 cycles per second, [*] very readily, but the output was very small. It was used mostly for telephonic work and for scientific investigations.
This [Fig. 11], if you please, is another small machine which I built, and with it I also obtained a very high number of cycles. You see how that was made. Here [field] I have 8 laminated magnets, and the circuit was formed through here, you see. On the rotating part I had 9 projections so that if, for instance, this armature was rotated, say, in the clockwise direction, then the magnets will come successively into play also in the clockwise direction. [*] But, as you will readily note, I had a very small electromotive force, for the reason that there was always the inductance of seven coils while one was generating the electromotive force. However, [the] inductance I could overcome resonance, in properly adjusting the capacity, so that was no objection, and the machine was extremely serviceable. This machine gives, by one revolution, 72 impulses -- 72 cycles, because there are 8 poles and 9 projections. That means 8 x 9 = 72. And of course, being small, light, and balanced, I could rotate it a very great speed and get a very high frequency.
Chapter XXXI - The Martin Book
"Massage" With Currents of High Frequency
I trust that the present brief communication will not be interpreted as an effort on my part to put myself on record as a "patent medicine" man, for a serious worker cannot despise anything more than the misuse and abuse of electricity which we have frequent occasion to witness. My remarks are elicited by the lively interest which prominent medical practitioners evince at every real advance in electrical investigation. The progress in recent years has been so great that every electrician and electrical engineer is confident that electricity will become the means of accomplishing many things that have been heretofore, with our existing knowledge, deemed impossible. No wonder then that progressive physicians also should expect to find in it a powerful tool and help in new curative processes. Since I had the honor to bring before the American Institute of Electrical Engineers some results in utilizing alternating currents of high tension, I have received many letters from noted physicians inquiring as to the physical effects of such currents of high frequency. It may be remembered that I then demonstrated that a body perfectly well insulated in air can be heated by simply connecting it with a source of rapidly alternating high potential. The heating in this case is due in all probability to the bombardment of the body by air, or possibly by some other medium, which is molecular or atomic in construction, and the presence of which has so far escaped our analysis—for according to my ideas, the true ether radiation with such frequencies as even a few millions per second must be very small. This body may be a good conductor or it may be a very poor conductor of electricity with little change in the result. The human body is, in such a case, a fine conductor, and if a person insulated in a room, or no matter where, is brought into contact with such a source of rapidly alternating high potential, the skin is heated by bombardment. It is a mere question of the dimensions and character of the apparatus to produce any degree of heating desired.
It has occurred to me whether, with such apparatus properly prepared, it would not be possible for a skilled physician to find in it a means for the effective treatment of various types of disease. The heating will, of course, be superficial, that is, on the skin, and would result, whether the person operated on were in bed or walking around a room, whether dressed in thick clothes or whether reduced to nakedness. In fact, to put it broadly, it is conceivable that a person entirely nude at the North Pole might keep himself comfortably warm in this manner.
Without vouching for all the results, which must, of course, be determined by experience and observation, I can at least warrant the fact that heating would occur by the use of this method of subjecting the human body to bombardment by alternating currents of high potential and frequency such I have long worked with. It is only reasonable to expect that some of the novel effects will be wholly different from those obtainable with the old familiar therapeutic methods generally used. Whether they would all be beneficial or not remains to be proved.
Previous Chapter --- Contents --- Next Chapter
THE TESLA EFFECTS WITH HIGH FREQUENCY AND HIGH POTENTIAL CURRENTS
Chapter XXV - The Martin Book
To the Archive Page Discussion on Tesla's Technology
Lab-Tesla disclosures on the technology just presented
Mr. Tesla's Personal Exhibit at the World's Fair
Chapter XLII - The Martin Book
Tesla's Laboratory Power
