Nikola Tesla - Free-Energy Devices

350 INVENTIONS OF NIKOLA TESLA.portant element than the frequency. When both of these aresufficiently high, the heating may be almost entirely due to thepresence of the rarefied gas. The experiments to follow willshow the importance of the rarefied gas, or, generally, of gas at or-the incandescence or otherdinary or other pressure as regardsluminous effects produced by currents of this kind.I take two ordinary 50-volt 16 c. p. lamps which are in everyrespect alike, with the exception, that one has been opened at thetop and the air has filled the bulb, while the other is at the ordinarydegree of exhaustion of commercial lamps. When I attachthe lamp which is exhausted to the terminal of the secondary ofthe coil,which I have already used, as in experiments illustratedin Fig. 179for instance, and turn on the current, the filament, asyou have before seen, comes to high incandescence. When Iattach the second lamp, which is filled with air, instead of theformer, the filament still glows, but much less brightly. Thisexperiment illustrates only in part the truth of the statementsbefore made. The importance of the filament's being immersedin rarefied gas is plainly noticeable but not to such a degree asreason is that the secondary of this coil ismight be desirable. Thewound for low tension, having only 150 turns, and the potentialdifference at the terminals of the islamp therefore small. WereI to take another coil with many more turns in the secondary,the effect would be increased, since itdepends partially on thepotential difference, as before remarked. But since the effectlikewise depends on the frequency, it may be properly stated thatitdepends on the time rate of the variation of the potential difference.The greater this variation, the more important becomesthe gasas an element of heating.I can produce a much greaterrate of variation in another way, which, besides, has the advantageof doing away with the objections, which might be made inthe experiment just shown, even if both the lamps were connectedin series or multiple arc to the coil, namely, that in consequenceof the reactions existing between the primary andsecondary coil the conclusions are rendered uncertain. This resultI secure by charging, from an ordinary transformer which isfed from the alternating current supply station, a battery of condensers,and discharging the latter directly through a circuit ofsmall self-induction, as before illustrated in Figs. 183*, 183&,and 1836-.In Figs. 186, 1865 and 186c, the heavy copper bars BB^ are