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INTENTIONS OF NIKOLA TESLA.

enormous, little is felt wlien the discharge is passed through thebody, provided the hands are armed. This is to some extent dueto the higher frequency, but principally to the fact that less en-ergy is available externally, when the difference of potentialreaches an enormous value, owing to the circumstance that, withthe rise of potential, the energy absorbed in the coil increases asthe square of the potential. Up to a certain point the energyavailable externally increases with the rise of potential, then itbegins to fall off rapidly. Thus, with the ordinary high tensioninduction coil, the curious paradox exists, that, while with a givencurrent through the primary the shock might be fatal, with manytimes that current it might be perfectly harmless, even if thefrequency be the same. With high frequencies and excessivelyhigh potentials when the terminals are not connected to bodiesof some size, practically all the energy supplied to the primary is

Fig. 105. Fig. 10(5.

taken up by the coil. There is no breaking through, no local in-jury, but all the material, insulating and conducting, is uniformlyheated.

To avoid misunderstanding in regard to the physiologicaleffect of alternating currents of very high frequency, I think itnecessary to state that, while it is an undeniable fact that they areincomparably less dangerous than currents of low frequencies,it should not be thought that they are altogether harmless.What has just been said refers only to currents from an ordinaryhigh tension induction coil, which currents are necessarily verysmall; if received directly from a machine or from a secondaryof low T resistance, they produce more or less powerful effects, andmay cause serious injury, especially when used in conjunctionwith condensers.