Nikola Tesla - Free-Energy Devices

046 INVENTIONS OF NIKOLA TE8LA.begins to appear. When the bulb is connected with the coil, thepiece of carbon, if small, may become highly incandescent atfirst, but its brightness immediately diminishes, and then the dischargemay break through the glass somewhere in the middle ofthe stem, in the form of bright sparks, in spite of the fact thatthe platinum wire is in good electrical connection with the rarefiedgas through the piece of carbon or metal at the top. Thefirst sparks are singularly bright, recalling those drawn from aclear surface of mercury. But, as they heat the glass rapidly,they, of course, lose their brightness, and cease when the glass atthe ruptured place becomes incandescent, or generally sufficientlyhot to conduct. When observed for the first time the phenomenonmust appear very curious, and shows in a striking mannerhow radically different alternate currents, or impulses, of highfrequency behave, as compared with steady currents, or currentsof low frequency. With such currents namely, the latter thephenomenon would of course not occur. When frequencies suchas are obtained by mechanical means are used, I think that the ruptureof the glassis more or less the consequence of the bombard,ment, which warms it up and impairs its insulating power but;with frequencies obtainable with condensers I have no doubtthat the glass may give way without previous heating. Althoughthis appears most singular at first,it is in reality what we mightexpect to occur. The energy supplied to the wire leading intothe bulb isgiven off partly by direct action through the carbonbutton, and partly by inductive action through the glass surroundingthe wire. The case is thus analogous to that in which a condensershunted by a conductor of low resistance is connected toa source of alternating current. As long as the frequencies arelow, the conductor gets the most and the condenser is perfectlysafe ;but when the frequency becomes excessive, the role of theconductor may become quite insignificant. In the latter case thedifference of potential at the terminals of the condenser may becomeso great as to rupture the dielectric, notwithstanding thefact that the terminals are joined by a conductor of low resistance.It is, of course, not necessary, when it is desired to producethe incandescence of a body inclosed in a bulb by means of thesecurrents, that the body should be a conductor, for even a perfectnon-conductor may be quite as readily heated. For this purposeit is sufficient to surround a conducting electrode with a non-con-